So instead of simply changing a lamp, they change the whole fixture. Presumably, if it's fixed, rather than just a plug-in thing like a floor or table lamp, they have to get an electrician in to do it. Or do it themselves and probably make a hash of it and maybe invalidate their home insurance or worse.
Sorry, no amount of explanation will ever convince me that
that is a sensible course of action
Oh yes, energy efficiency. L*D's may cost less to run, but when you take into account the materials used in their manufacture and the potential problems involved with the disposal of said materials, one thing they are
not is 'green'