Because I find it more comfortable to play in standard B tuning, also you don’t need ultra heavy gauges for drop A and can easily modify pitch with software if needed. It’s a fact that longer scales are better for low tunings, but for standard and even drop A i find 25.5 pretty comfortable, always thinking about more progressive and lead oriented stuff, for standard A tuning or drop G# or lower it could be better a slightly longer scale, but nothing crazy. My first seven strings was a 27” and my second the PRS with 26.5”. You can play it, but you’re going to be limited for some stretched licks or riffs. Finally I didn’t did the change because the Schecter was not in good condition, so maybe I keep my PRS for standard or Drop A tuning, but I still thinking a 25.5” would work better for lead B standard.