Life pro tip: most recruiters can't write emails that look like they came from humans rather than spambots. If you're actively looking for a job, check all your spam folders daily. I can't tell you how many actual job leads have ended up in mine.

Also, recruiters sends large numbers of similar emails so they look like a spammer to the filters. Then if people who get them just mark them a spam rather than deleting or responding, the problem is compounded.

Depending on your definition of spam, the recruiters might actually be sending spam. I once had a recruiter try to hire me for the company I was already working at and had clearly indicated on my Linkedin...

People who get them might not have opted into them. That is spam, by definition. Elephant in the room of "foot-in-the-door marketing"? I guess.

I received recently one of the most bizarre emails via gmail: one email completely written in Chinese. I was curious precisely because it didn't go to the spam folder. After running it through Google translate it actually looked like a legit job offer. What a pity life is so short and I have so many responsibilities, it would have been cool to grab a laptop and just go.

Many recruiters are sending their emails from a system, not writing them by hand. They look they came from a template, because they did.

Add to that that when that recruitment system was implemented, the recruiter probably didn't bother updating/customizing the default templates, making their emails just the same as everyone else's.