When being dealt a big pair preflop, there is tendency for players looking for big action to want to try to disguise the hand and just limp in. Such as having pocket aces under the gun, it can feel strange to have to raise right off the bat, alerting the whole poker table to the fact that you just might have the rockets. It can be a dead giveaway, and so disguising that condition is often a good way to trick the table into going broke with the right flop.
The problem with limping with big pairs early is that when you don’t get raised, and the flop comes cheaply, you never know what you are up against. With the small and big blinds coming in with literally any two cards, it can be impossible to tell whether you’ve been outflopped, or if you are getting raised by someone who has just top pair and thinks they have you beat.
If you limp preflop with a big pair, you should be ready to let the online poker hand go in spots where the price and texture of the board outweighs your holdings. The limp move is a gamble, so unless you are prepared for a wild ride, you might as well just raise out of the gates. Keep this in mind at the casino.