All I ever see is "if you're the first one entering the pot, RAISE." Either raise or fold, but never limp.
Why? What's so bad about limping/flat calling? Is it absolutely never a good idea?
A number of reasons,
you need to raise to thin out your opponents, it's harder to win against multiple opponents!
It helps define opponents hands, if you are reraised after raising, saying that you have a hand then they are telling you they have a very strong hand, if you're raised after limping they're range is going to bet a lot wider!
It builds a pot worth winning when you have a strong hand,
You can cbet the flop and hold on to initiative in the hand,
You can exploit players who begin taking a stand against your aggression,
You don't instantly mark yourself as a fish leading to the better players at the table targeting you(maybe this what you want though)
Well, its because rookie players often limps, because they are not sure about raise.
Its actually other way around. You should be dam sure why are you limping. If you are not sure, better raise.
E.g. how will you narrow range of BB? With limp, you will loose with you KQs against 63o. And you will loose big pot, because you will not expect such hand at your opponent.
Raise gives you reasonable fold equity (to get money without risk). At some tables, those money are big part of your profit. With limp => no fold equity.
Rookie: raises with monsters, limps with mediocre hand => BAD
Better: raise with monsters and some interesting hands. Fold mediocre hands.
Mediocre hands are BAD BAD BAD. Like KJ, KT. Why? Because you will in 50% win a small pot and 50% loose a big pot.
Better fold such hands and use 89s etc.
What if I want to invite other players to come into the pot with limping or small raises to build pot odds against multiple opponents incase I hit the flop hard, maybe with suited connectors?
What if I have a big hand like Aces or Kings? Don't I want multi-way action with a big pair (to take a flop 3-handed or more)? I assume there's bigger pots to be had with a big pair if I get multiple callers as opposed to getting heads up.
41.89% to winfor example AA vs JTs vs 44 vs 22 vs 73o: You don't even have 50% equity preflop which means you're going to lose by the river more than half the time.