If I'm a salesperson looking for my next gig you're going to have to prove that you're paying a high enough commission for it to be worth it to me.

But most importantly, why would a salesperson who can make a $15k commission immediately work someplace where they need to wait for the sales and billing cycles to complete? That could easily be 30-60 days after start and will put you tens of thousands in commissions behind your competitors. And if a salesperson quits or is terminated do they still get commissions 30-60+ days in the future? Unlikely, especially if there's any bad blood.

From a business standpoint it's easier to pay on unrealized revenue and decrease the overall commission amount such that it's still profitable even when you're paying commission on money the company doesn't see.