AT flops a flush draw - how to play?

[AlphaWice]

I noticed both repliers told me to raise preflop. This is completely against my line of thinking. Why raise preflop? I believe my ace is too weak, and I am only limping in late because of the flush draw (with ATo I would fold outright here.) Is this a strong leak in my game? Can someone explain whether it is good to raise PF here with ATs, and why?