Often you don't need more than you have, and its nice to have fixed costs. An example - you buy Photoshop or Lightroom, and they cover 100% of your needs. As long as you can run it, you are happy with what they provide. Well apparently that didn't generate enough cash for Adobe but that's a long story.

Tons of businesses uses commercial software with little need of support in form of some patches. Usually toolsuites are mature and they don't try to hack every last bit of it.