Some publishers only allow authors a limited number of e-prints which soon go, so one has to say 'no' to requests. It seems insensitive to have no option but to decline the request without giving a reason.
Dear Alan Dobson Have a look at https://www.researchgate.net/post/How_do_I_ensure_that_I_am_not_infringing_copyright_if_I_send_a_published_article_that_has_been_requested_in_Research_Gate It is perfectly fine to send people requesting the full text of your paper a pdf file of your paper. This is not infringing any copyright issue (making a publicly available version is prohibited).