Baffling. This really is like buying a billboard with your phone number on it, along with text that reads "contact me!!" and then getting upset that you're getting phone calls.
The whole point of associating an encryption key with your email address on a public keyserver is so that you get encrypted mail!
Many keyservers don't verify you own the email address. Someone else could have uploaded a PGP key for your email. You shouldn't trust the value in the keyserver without additional confirmation via another channel (like giving someone the fingerprint in person).
And PGP/GPG keys are used for more than just email, so just because you have a key on a keyserver doesn't necessarily mean you want your emails encrypted with it.
I just wanted to say that clearly keyservers needed to add this (both verification and specifying the purpose of the key), but clearly they have already done so.
I'm not surprised; these people think a lot more about these sort of things than I do.
One possible addition might be that maybe you could specify whether people should use the key to encrypt whenever possible, or only when security is absolutely vital. That's a setting that could pass the decision to encrypt to the sender (if clients support this).
The whole point of associating an encryption key with your email address on a public keyserver is so that you get encrypted mail!