Clever spammers (there are some!) see the presence of company@<domain> and assume the user will have similar emails for other accounts, so it might be worth trying ebays scams to ebay@<domain> or banking scams to chase@<domain> or boa@<domain>. Sending is cheap so why not, you're not trying to fool everyone, only a few.

I use a unique string per company but it's not guessable in advance, but it's obvious when looking at it and squinting a bit, for example (and these are not the exact ones I use): sundclod@<domain> or ebuy@<domain> or amzoon@<domain>

Sure I have to remember them but it's easy for me to check and my password manager is filling them in for me 99.99% of the time.

I can filter on those emails instead, and I also know that anything coming to soundcloud@<domain> or ebay@<domain> or amazon@<domain> is definitely spam as I've never used those addresses myself.

If sundclod@<domain> appears in a leak I can (hopefully) change my account email at Soundcloud to sondclud@<domain> and then confine sundclod@<domain> to /dev/null