StubHub is owned by eBay, who is in process of trying to sell them. Ticketmaster merged with Live Nation some years back.
The team sold the tickets to the person who is listing them, so it's not like they aren't getting paid for the seats. If you're finding deals below face on a secondary market, the person who you're buying from is the "loser" in the deal so to speak. As long as the teams get some butts in the seats, people paying for parking, buying concessions/merch, etc. (And also these killer TV contracts), they can roll with it.