Because I also wouldn't risk a cycle, and several thousand dollars, by not getting my butt in gear well before the summer solstice.
I lost a cycle because the stars just didn't align for me last year with the onset of COVID, so maybe that was part of it, but I wouldn't (and didn't) sit around all summer and then decide to shoot my shot in September. If circumstances caused me to not be in a position to apply until September, I'd save my money for the next cycle.
There is no reason for it to only be one school, and it's not $70. At Pritzker alone it's $42+$85=$127. No, I wouldn't skimp on an expense, like a business suit, that might make the difference between success and failure. That's very different from applying to any or all schools in September. That's very likely to just be throwing money away, and could be avoided by applying earlier in a cycle.
You're 1,000,000% correct about not asking "what if?". This is high stakes poker, and that's why I spent months thinking about where to apply. I ended up applying to plenty of schools where I don't think I have a realistic chance, spending probably over $1,000, in addition to what I was already spending, just to never wonder "what if?".
But I did it in June and July, not September. By September I've made my peace with my decisions, and I'm not really receptive to mass e-mails from a school looking to increase its pool and perceived selectivity. I'm also not going to be buying any Powerball tickets this week, notwithstanding multiple mass invitations to do so, thereby guaranteeing I won't be the next Powerball multimillionaire. But, I'll have saved my $2! 😎