I think most part of people just do this because they don't study enough and/or they don't apply what they have learned...
So I don't have limp in my normal repertoire..
But, in Texa's Hold'em, I can understand limp in some specific moments, let's try to remember 2 of them:
1st – Small blind (you) vs big blind (opponent), it's possible to limp sometimes, specially when you are playing against a very aggressive player who 3-bets you more than the usual (or more than your field does), for example.
2nd – Imagine yourself at BTN (9 players table), you have 87s, CO and HJ limped (both are donkeys) and SB and BB are more passive than they should, why would you try to isolate CO and HJ with 4.5bb (for example) or fold your medium suited connector? You could just limp and try to find your hand's equity after flop being IP and playing against bad players who are extremely predictable and manipulable.
[This all is just my own opinion, based on my own learnings, but you all can deny it if you not agree with me]
