I've been here for a while, this is accurate. If there were no limit, you could technically upvote all of the things you really like instead of having to conserve or bookmark topics to upvote later. However, there are lots of people here who would be eager to downvote almost anything in sessions over a grudge or because they got upset, and its dumb really. I agree with the value part as well, it does make every upvote feel a bit more special since anyone can only do so many per day. Perhaps in the long run it did do more good to help inspire users to create, rather than people feel like they're being held back from showing appreciation with a like button.
Also a bit true since I'm pretty sure every upvote and reply to a post does create a notification, and seeing a constant flow of notifications from one user may seem distracting or off putting.