As a newer user, I am uncertain if the community norms here in CV are different than on Math.SE. There, it appears to be acceptable to ask a user to accept/upvote an answer in cases such as your having posted the only answer and the OP commented that it was helpful (see here). Does that apply here on CV too?
Users failing to respond to good answers by accepting one is annoying, there's no doubt of that. I've seen some wonderful answers go unrecognized by the poster of the question and the lack of response (either accepting or explaining why there are outstanding issues that would stand in the way of it) often strikes me as selfishness in the face of an answerer's generosity. Some regular contributors seem to suffer from this non-response to their efforts shamefully often.
(In my own case, even when I felt that an answer didn't really answer my question after several attempts to convey the issue clearly to them, I have accepted an answer as clear recognition of the answerer's sterling efforts in responding to it.)
I think in the case where the OP explicitly acknowledges an answer as helpful it's more than reasonable to point out to them that accepting the answer is an option - even in respect of your own post - many new users miss that this feature exists (or forget it) and are often grateful for the chance to put their thanks to that poster in more concrete form.
Where there are several good answers that attract many upvotes, one might reasonably encourage the OP to consider choosing an answer. (I don't think it's reasonable to place the onus for encouraging others to understand the way stackexchange works only on the moderators. The responsibility falls to all of us.)
If you aren't only generating reminders on your own responses, but more generally encouraging people to 'follow the site culture', I think it's a very positive behavior.
We sometimes encourage negligent posters to review how the site works and, in particular, to accept good answers if they can. This is a task that high-reputation community members often take on. When you politely address this general behavior it does the site some good.
A large number of the requests to accept an answer that I have seen come from people whose answers aren't that great in the first place: they are effectively rushing or even bullying the OP into a premature acceptance. People notice when you do this and if you do it too often you may acquire an "invisible" negative reputation. This amounts to a sense among the frequent voters in the community that you are in this only to drive up your reputation. It would only be natural for them to tend to cut you less slack and refrain from upvoting some of your marginal posts. (Some folks might enjoy doing a tongue-in-cheek Bayesian analysis of this phenomenon :-).)
If, after a suitable period of time (several days at least) you have posted an answer that, based on community votes, is clearly superior to the others, then you might post a comment that subtly reminds the OP of the value of marking one of the answers as accepted.
Yes; I also think it's reasonable to ask even if they don't comment—ask them to accept an answer or explain why it doesn't help them. But we do get a lot of users who appear once to ask a question & don't come back again once they get an answer.
[@whuber's answer includes caveats I hadn't considered (in fact I haven't noticed such bad behaviour on CV), but of course fully agree with.]
Quite apart from community norms and the optics of begging for reputation, accepting an answer also visually marks the question as “answered” (which means “no need to spend more time on it/check it” if you are looking for something to do and also “likely to provide a solution” if you are searching past questions to solve a problem you are having).
A lot of the discussion seems to focus on quality and reputation but in my mind the answer doesn't even have to be great or especially deserving to be accepted. If it provides a solution or somehow addresses the question (which might itself not be particularly deep or interesting), then the question ought to be marked as “answered” or the OP should explain what's missing.
Unlike upvotes, it's not so much about the reputation than it is about site management and good record keeping. I often ask people to consider accepting an answer (my own or someone else's) or to “upgrade” short comments to a full answer for this reason (it's not uncommon for a brief comment that seems unremarkable to its author to fully and completely address a question).
Encouraging (pressuring - yes, it can be viewed as such) users to accept an Answer has been outlawed on StackOverflow for good reason. It is up to individual users whether they want to accept an answer or not. If they don't want to, that is up to them.
For example, the accept rate is now not displayed for a user in the Q&A to stop people berating users that have a low accept rate.
A timely reminder of how the SE sites work via a link to FAQ is OK for new users, but doing so for every unaccepted question would just clutter the site.
Other than that, vote on good Answers, downvote or comment on bad Answers, users visiting those Questions will be informed by the voting even if an accept is not forthcoming.
Finally, I don't buy into the idea that once an Answer is accepted the Q&A is complete. A better Answer may be forthcoming, or an alternative approach or solution provided. I often check back against interesting Q&As through the Favourite mechanism to see if there have been updates. CV, like the other SE sites, is an evolving beast, and that doesn't end with a click on the tick.