The 1500 hours rule was just a political "let's do something with no sense" after the 2009 Colgan Air accident, were fatigue and poor cockpit discipline were also contributing causes.
You know what's also funny? That both the involved pilots had more tha 1500 hours at the time of the accident.
So what's this 1500? Just a random number written by a politican, nothing more than that.
I'd also like to know why a bachelor program would make that 1500 become a 1000...that's one third of the "essential" required experience waived. Or why pilots with less than 1500 hours performed better than guys with more than 1500 hours during regional training. Or why are they considering to lower the magic number to solve the "pilot shortage"...
We should look at the quality of training and personal attitude, not at total hours.
My personal view about increasing T&C and the "pilot shortage" in the US: they're not related to the 1500 hours rule, but to the fact that a lot of people choose other careers when the regionals were paing 20000$ for an FO. Now they're forced to increase T&C. Then it will cycle again and again.