Windows 7 share depends on niche you sell your software in, but it is still pretty high, so not supporting it is losing money, IMO. In my case, supporting Windows 7 does not require any additional effort - if you won’t be using any APIs that are only supported on Windows 10+, then you should get Windows 7 support automatically with no additional effort.
Another story is Windows XP. While severely outdated, there are still people who use it. Writing Windows XP-specific code is not practical in economic terms, so we simply offer partial support for Windows XP - some features do not work and require newer OS - it is a tiny subset of features, and in most cases users do not hit those limitations. We have Windows XP listed as a supported OS on the web site. Windows XP share is about 5%, and this is good money I better not lose