Do you not have a bank account?

Not yet for my startup/side project, no :/. No business number either.

Why not use your personal bank account?

Yes, I could use my personal bank account. I guess the real blocker is the business number.

We don't require a business number of any kind, you can sign up as an individual (the question will be "business type", and individual is one of the options).

I did this the first time I used Stripe, in a little project where I was mainly gauging interest for whether I'd persue it further. Just opened up a second checking account and linked Stripe to that. No cost or pain for me.