All of these are examples of the need of multiple on-line identities. You wouldn't use your main email for two projects or two employers that you don't want to

All of these are examples of the need of multiple on-line identities. You wouldn't use your main email for two projects or two employers that you don't want to know each other. Surely someone you freelance for has your address already? Your primary address probably has traces of your real identity all over the Internet, including orders from eBay and others, so an adversary could dox you in an instant anyway. Especially if you use it for work related things. So why not make it easy to contact you?