This is more "home networking" than "homelab," but I imagine the people here might be familiar with what in talking about.
I'm trying to understand the logic behind ISPs offering asymmetrical connections. From a usage standpoint, the vast majority of traffic goes to the end-user instead of from the end-user. From a technical standpoint, though, it seems like it would be more difficult and more expensive to offer an asymmetrical connection.
While consumers may be connected via fiber, cable, DSL, etc, I assume that the ISP has a number of fiber links to "the internet." Those links are almost surely some symmetrical standard (maybe 40 or 100Gb). So if they assume that they can support 1000 users at a certain download speed, what is the advantage of limiting the upload? If their incoming trunks can support 1000 users at 100Mb download, shouldn't it also support 1000 users at 100Mb upload since the trunks themselves are symmetrical?
Limiting the upload speed to a different rate than download seems like it would just add a layer of complexity. I don't see a financial benefit either; if their links are already saturated for download, reducing upload speed doesn't help them add additional users. Upload bandwidth doesn't magically turn into download bandwidth.
Obviously there's some reason for this, but I can't think of one.
Apart from the technical reasons already mentioned, before things like Twitch and TikTok and Instagram were a thing, people mostly downloaded content and very rarely uploaded much. So it made sense for the ISPs to allocate more downstream channels and advertise much higher download speeds which is what everyone cared about. Especially with DSL and aging copper lines, it kind of tops out at 40-50 Mbps for most people when lucky (even though VDSL2-Vplus technically can go up to 300/100). Especially if you're shoving IPTV on that line, 25/25 is much less desirable for the average consumer than say, 45/5.
And as others have said, it's much easier for the ISP to throw more power on your lines to sustain faster speeds, so it just kind of happened that it was convenient for everyone to do it that way.
It also has the side effect of heavily discouraging hosting servers at home, reduces the amount of bandwidth used by torrenting and the likes.