Although there is a good % of the market that works in a similar way to your business, it is worth noting that when a deal is exceptionally good, executives will create exceptions. MS Suite and some of its satellite offerings (PowerBI,Sharepoint,etc) is a good example of an exception.

There are also cases where a company will pick multiple vendors in an attempt to de-risk and/or for negotiating tactics. If you are fully dependent on a single vendor, the cost of migrating tends to skyrocket and the negotiating power moves towards the vendor.