Gmail labels are great but they’re not universal, and are easy to strip out.
A lot of sites:
- Don’t allow +'s in email addresses
- May let your register but then not login
- Are aware of labels and simply strip them out
I have an email address I have only ever used with labels but still get spam to the non-labeled address. Spammers and email harvesters are very much aware of this trick, so it only works on legitimate sites.
There are plenty of them, just wait!