I thought the same but in my experience, I've rarely, if ever, had the need to search for email. When I did (super rare), I found that the search function in gmail was mostly busted. Sometimes it would omit results for email that is clearly there that match specific queries or filters. I'd have to try several different methods and even manually going back at times to get the email in question. In the end, having it overloaded with email was more of a pain for those instances where I needed to find a specific email.

Sometime towards the end of last year, I decided to wipe my entire email record (which was a lot) and start from a clean slate. Since then, I made an effort to delete any unimportant emails instantly, file the important ones I think I may need to keep, and tag temp emails that needs to be there but would be deleted once they serve their purpose (for example, online orders for items shipped).

For several months now, I've managed to keep my entire email account under 50 emails. It makes managing it much easier and great for emails I would need. This of course is base on my habits. I never really have a need to pull up the majority of old emails and leaving it there is just unnecessary clutter (personal opinion).