We are quickly running out of .com and other TLD's that are clearly represent what we do. Many web/mobile apps are now resorting to somenameapp.com as a way to use a TLD for their given choice of name. having a TLD means it's easier for a start. But also when running a TLD you can stipulate the rules for purchase and use. Allowing us to prevent domain hogging, and keep the space clean for applications only.
The cost of screening apps manually will make it prohibitive in cost as a TLD. It's a catch-22, speculators actually make the registries a ton of cash. They love speculators. From a registry perspective, speculation IS a business model.