Not sure about VC, but I know for a fact the private equity firms do this.

It's usually in the context of a "standard operating procedure."

I worked in two companies owned by a leading tech PE firm, and they had a standardized tech stack (with specific vendors) that we were expected to use. Using anything else needed to be approved. This was actually a good thing, because..

It came with enormous discounts. Be prepared to have an incredible value proposition AND discount like crazy.

If you can pull it off, it's a consistent flow of clients without sales acquisition costs.

Yes, they do. However, this happens in rare case as they generally have their own team.