In an average city block, I'd expect that ~99% of displays—TVs, monitors, projectors—would support HDMI-in. Plus A/V receivers, for that matter.
Maybe, maybe 5% would support DisplayPort over USB-C (or anything else that lets you use USB-C for video in), and that's after a few years of Apple pushing it as The Next Big Thing. I fully expect HDMI will be more common than DP+USB-C in five more years, and quite likely in ten. For one thing, it's really nice to install in offices and houses because you can have long runs of it (50+ feet), with relatively cheap cable (compared to video-capable USB-C, certainly) and it'll still work. If something replaces it, I think it'll either be wireless or some other cable, not USB-C.
To be clear, I'm explicitly not commenting on market penetration of either solution, but rather their inherent capabilities. I don't see USB-to-HDMI cables or adapters as particularly cumbersome, whereas there isn't a way to just cram a storage module fully inside a USB-C port as though it were an SD slot.
As far as the cost of HDMI vs USB-C for long runs, that's a good point. I could see similarly cheap/efficient video-only USB-C cables potentially addressing that use case, but I don't know enough about the internals of USB-C to comment on whether that's viable. I could also see HDMI being used only behind the scenes in the future (like how computers don't typically have fiber optic or coaxial ports).
At the end of the day, it's not like I'm suggesting that HDMI should be removed from computers. My point is that the argument for removing it (whether or not you agree with that argument) never applied to SD ports in the first place.
USB-C monitors aren't particularly common and it can be hard to find good ones. I don't think LG makes their 5K Ultrafine anymore, but they still make 4K monitors with USB-C video. It's pretty convenient because one cable connects to the monitor and provides power to the laptop.
But only on much shorter cables (up to 1 m) than normal size DisplayPort or HDMI.
In my home, I use 2 monitors. One of them is close enough to the laptop so that an USB-C cable can be used. The second is too far away. If the laptop had no DisplayPort or HDMI, I would have needed a dongle.
Those include the USB-C to HDMI converter in the connector, instead of in a separate dongle.
It is more convenient than the separate dongle, but not as convenient as having a HDMI connector on the laptop.
If you have HDMI on the laptop, you might find a HDMI cable wherever you go. With only USB-C, your only chance is to always carry with you the USB-C to HDMI converting cable.
