I think it depends. Let's say I sell my finance application to an organization with 10k employees. They then use it to handle transactions on around 100mil per

I think it depends. Let's say I sell my finance application to an organization with 10k employees. They then use it to handle transactions on around 100mil per month. If there are bugs, it may result in money being transfered to the wrong company, or money being transfered without proper approval. Maybe unlikely bugs but could happen. I can show a banner telling each of the 10k users about browser requirements. I guess that around 99% of the users will ignore that banner and happily proceed with unsupported browsers. If I don't know if it will work with the browser they are using, why should I let them perform transactions using it? Sure, if it goes wrong maybe I can tell the CFO that their employee ignored the banner, but that won't make him happy. For me selling the service there are zero benefits with allowing arbitrary browsers.