Spammers simply obtain lists of emails through hacking or purchasing them and then spam them, they don't pick a particular address and modify it.
But as a counterpoint it literally happened to me to me years ago when I used to use name+<service>@exmaple.com. I got cold emails to 'name+paypal' despite never, ever having used that localpart. I've no doubt it was absolutely targetted and not a hit-and-hope spamblast but it was enough of a wake-up call for me to realise it couldn't really be relied on.
I used similar (well, plus addressing with localpart=name+<service>) a long time ago and once got emails to name+paypal@example.com even though that was a suffix I'd never used. Some enterprising person out there had obviously obtained one or more of my service-specific addresses and was trying to game my attention by changing the identifier to something 'important'. That's when I personally ditched the approach.
