It's an arbitrary number devised to make the lowest common denominator pilot halfway experienced by the time they fly 121. That said, I don't know any pilots who agree with it on safety grounds.

However, I'd argue it's a good thing for pilots for a totally separate reason. Hopefully it cuts down on the pilot supply enough that in 1, 5, or 10 years pilot wages start significantly rising and we'll have real leverage for once during contract negotiations. Many say the shortage will never happen, but it certainly won't if hiring mins go back down.

Yes, 1500 sucks for a lot of guys when they have to pointlessly instruct an extra year and a half to reach it, but in the long run it will be substantially better to weed out the people who aren't serious about this profession so that we can become a rare and precious commodity and be paid accordingly.