It's one thing to have 50 state databases of voter information, each state with its own rules as to what is available, what the fee is, its own paperwork, etc.
It's quite another to have one central voter database.
Hackers can be lazy, also. They'd rather break into one system than 50 systems.
Further, regardless of whatever high-flown rhetoric and mission statement the "election integrity" commission dresses itself up in, its mission is clear: Prove that 3 million or so people voted illegally, that they were all Clinton voters, and therefore, Trump is the winner of the popular vote.
Because Trump needs to be loved.
A president with a normal sense of self-acceptance would simply say "Hillary Clinton won the national popular vote by 3,000,000? I'm president. She's not. Next!" "My critics don't like me? Run someone better next time. Next!
But Trump needs affirmation at all times. Trump always has to win it all. Look how he's treating AG Sessions for not being loyal enough to Trump.