But for me (I use AppleTV vs. Roku), it's because TVs are SLOW (IME). Clicking on Netflix takes about 5 to 10 seconds to open. Clicking down on the remote takes 2 to 3 seconds. It's even worse now that Netflix does that live preview when the cursor sits for a spell on a title. And finally Netflix crashed on my TV 3 or 4 times during the week that I tried to use it.
I looked long and hard to find the best option for a dumb TV without Wi-Fi, without Alexa, without Siri, without any of that, because I don't actually want to stream anything to it and I don't want my television to be a hackable portal between my home and family and any hacker able to exploit bad firmware. No regrets.
In addition to trusting Apple (Apple TV) more than any TV or TV OS maker, models and firmware seems to be abandoned quickly. I’d rather decouple the UI upgrade cycle from the hardware upgrade cycle. Roku seems to support devices longer than the other TV OS makers, but they have “features” that I’d pay to not have (like ACR and https://support.roku.com/article/360021142813).
And it is so easy to hit the ESPN or 3 other "app" buttons on the remote so that can be annoying if you aren't careful picking up the remote or setting it down.
But overall yes, HDMI-CEC solves the remote issue overall except for the fact Roku poorly designed the remotes IMO.
Personally, I have a RPi running Kodi, plugged into $anytv (quite literally, no idea what the model is, as long as it supports HDMI).
TL;DR: because not everybody is you (i.e. has same requirements and preferences). Deal with it.