An "all-in" strategy ?

[jat850]

I play live 2/4 and I see a lot of people going "all-in" and then reaching in their wallets for more cash to keep playing. I am still pretty new, but I admit I do not see any advantage to this style of play. If you catch a good hand and go all in, the main pot is small and pays the rake. Am I missing something? Or is this style of "all-in" play a sign of fresh fish being self served at my poker table and I should keep a skillet warm? Enlighten me please.