I'm not going to address you obtaining a primary residence loan and renting it out as @Jon Holdman has hit the nail on the head with that.
Why do a lease option? Money.
You need to compensate for the added risk (of losing a rental).
If the market price is $1,000 (you didn't specific so I made up a number) and you can do a lease option for $1,200 then you are being compensated $200 over market.
If the value of the house is $120k and you do a lease option at $130k, you are coming out ahead $10k if they actually buy.
I agree that there are predatory lenders doing this, but it doesn't mean you can't make added profit by giving the option, just compensate yourself for the option.
And yes, you also have backdoor equity on the default or them not following through on the sale.
Many people aren't in the financial position for traditional bank financing. Lease options give them A PATH to home ownership. It's up to them if it is the correct path.