Hard to say why they aren't doing it. It's possible there's some exception in place. There would be absolutely no incentive to them not taking a deduction for their expenses.
But it's just as likely that they have a poor understanding of their requirements and are just not doing it. The penalties can be quite harsh if the IRS catches that, but at the same time, it's also fairly common for companies to overlook 1099s.
Regardless of whether or not you receive a 1099, it is your responsibility to track and report this income on your tax return. A 1099 makes that easier for you, but not getting one does not exempt you from your income reporting requirements.