Just want to add up that if people cannot keep track anymore on how many websites they registered their email, they can use the website "Have I Been Pwned" to tell if their email address were involved in a certain data breaches.
I had an old email address (not used in this forum of course) that became victim of data breach and now I realized why my Facebook back in 2009 was always being password changed.
I am pretty sure that many of us here are already aware and careful of how we use our email address to different websites, so I would just put this out to people that aren't aware yet.
Unless you plan on using a website for a long time, just use a temporary email address, and then this eliminates any issues that could come from that. Ideally, you wouldn't be using the same password anyway, and therefore that wouldn't be compromised. Obviously, data that you give that website could potentially be compromised, and therefore associated with your email address, which an attacker could leverage or potentially gain more information to carry out a more sophisticated attack. So, there's definitely could reason to use different emails if you do use multiple websites.
Personally, I hardly sign up to anything these days. Kind of sick of every website requiring you to give your data over by signing up.