SignalHire was the one I used recently, and Jigsaw was the one before.
Basically whenever a friend of yours installs some shitty free app on their phone and it demands to exfiltrate all their contacts your email address and phone numbers get scooped up and sold to the highest bidder. You can guarantee Tim Cook has a bunch of friends, grandmas, etc that have no idea how to use their phones and have 400 apps installed all syphoning off Tim's contact details.
Basically whenever a friend of yours installs some shitty free app on their phone and it demands to exfiltrate all their contacts your email address and phone numbers get scooped up and sold to the highest bidder. You can guarantee Tim Cook has a bunch of friends, grandmas, etc that have no idea how to use their phones and have 400 apps installed all syphoning off Tim's contact details.