Lets take Figma as an example, Imagine you have 1000 employees, 300 of them need Figma, so you are paying 120k per year in Figma licenses. You can afford 1 employee working on your own internal Figma. you are paying the same but getting 100x worst experience, unless your 1 employee with CC can somehow find and copy important parts of Figma on his own, deploy and keep it running through the year without issues, which sounds ludicrous.
If you have less than 1000 employees it wouldnt even make sense to have 1 employee doing Figma