That's not really where the problem lies. It lies in the choices made when developing the site. "Do we use a framework or feature that isn't part of the HTML standard to force users to use the subset of browsers that support that or do we use one of the many other options that do follow the standard?"

It wouldn't surprise me if those choices are being made by some web devs because those high up don't even think about it and those implementing it don't think much about the standards and just do it the way they do it because it's easy or that's just the way they know how to do it.

Governments (and their agents) shouldn't be choosing proprietary options that force people to use a specific company's resources.