You're right about that. But sometimes the only way to get a pay raise is to get a competing offer. It is a risk to ask your new employer to file for a H1 transfer and then back off (at the risk of pissing them off). I haven't done it personally, but I know a lot people do it.

I usually drop hints about a pay raise or change of responsibilities and if my manager doesn't oblige within a reasonable amount of time, then I know it's time to leave. It's nothing personal, but if someone else values me more than my own employer I'd rather seek greener pastures.