Why are the spam settings so poor?

[#1]

I have two or three companies that have my email address and who I try to block but I still get dozens of emails from them every day.
I was previously with BT and they were generally rubbish but at least they had a proper spam blocker.

[#2]

If you go to here https://portal.plus.net/my.html?action=myemail&s=1&redirected=yes&?membermenu=emailsettings
Select Manage My Mail
then
Spam
at the bottom you can white list or blacklist addresses which does work