It's disrespectful because I never consented to giving their company my email, nor have I consented to their services. This type of reasoning is why a vast majority of people never answer their phone, because there is a very large chance it'll be a phone call from a spammer/scammer.
I have no issues when I purposely choose to work with a recruiter, but invading aspects of my life when they never got permission to IS disrespectful.