The thing about SaaS is once you've found those first ~100 customers to give you money, this is a big indicator that your product solves a real problem, has found a place in the market, and will continue to grow. It's really hard to get those first 100 customers, but once you get them, incredibly easier to get the next 100.
Whereas if you're salaried at $48k/yr, the chance of getting a $48k/yr raise, and then another, and another, and 10x'ing or 100x'ing your compensation is effectively zero.
This is speaking from experience, I run a SaaS company currently making $60k/mo, and not too long ago we were making $4k/mo.