Because apart from the popup you eventually unconsciously dismiss every x number of saves, there's no reason to pay up.
I've been using it for 4 years unpaid, sublime has helped me get my first home. If I was forced to tomorrow because I could no longer use it I'd pay for it immediately, but right now there's nothing pushing me to part with my cash.
You could have validated this idea (for next to nothing, I might add) before quitting your job and investing all of your savings.
There's a lot of good reading out there around how to do what you've tried to do here in a safe and sensible way that doesn't waste time and your own hard earned money, but you seem to have ignored all of that. I suggest you purchase a copy of http://theleanstartup.com/
I genuinely wish you all the best of luck, but the way you've gone about this seems to me to be very, very foolish. Reckless even, given you have a family.