Vendor lock in contracts exist to ensure the business selling their product has secure revenue for awhile. I've always felt the most ethical way to run, even as someone who works for what a vendor, is to simply have a better product than the rest of the market, and make sure that your customer success team keeps your clientele happy. Vendor lockins seem pretty predatory to me, but I get why they exist from the view of the vendor wanting to secure revenue
If you're constantly working to improve things (Not screw with the design of your tool, but actually improve) based on your customer recommendations and research team, a company shouldn't need to worry about having vendor lock-ins nearly as much.
Also, all companies should offer a free trial/proof of concept to try out their tool before any kind of contract is signed, and if I was in a position running a business and a vendor wanted me to buy without trying first, I'd run.