Some places are wanting to go dual 5 GHz radios on APs (for general client density) rather than 2.4 GHz and 5GHz radios but 2.4 GHz only IoT devices force you into keeping a 2.4 GHz radio infrastructure active. These kinds of environments tend to turn the power down on 2.4 GHz anyways as "goes through walls" can actually be a bad thing for coverage when multiple APs are at play (SNR is more important than raw power).

For a typical consumer home use case continuing to use 2.4 GHz is most likely ideal though. Though some apartment complexes have such bad 2.4 GHz interference even that might not be universal.

In my opinion 2.4GHz is rapidly becoming a non-starter. Companies like Eero, TP-Link, and Spectrum are using 40Mhz wide swaths of 2.4GHz for their Mesh backhauls. Sitting in my home office in a single family detached home, I can see 24 different SSIDs all running 40mhz on the 2.4GHz band with 7 having a signal strength greater than -80dBm.

5Ghz doesn't propagate very far and putting IoT devices inside your home on 5Ghz makes a lot of sense. With 6Ghz coming on line and being reserved for high bandwidth applications, 5Ghz for IoT makes even more sense.

It's not the peak speeds, it's the spectrum use. The 2.4GHz ISM band has 100 MHz of available spectrum, the 5GHz wifi spectrum is 740 MHz wide, and is still occupied by fewer deployed devices.

To an IOT application, it's the difference between chatting with a friend at a quiet outdoor cafe and trying to shout at her in a crowded bar.

YMMV but in my house, with a commercial-grade wifi AP, I found that devices on 5 GHz get much better speed and range due to all the local noise on 2.4 GHz.

Pop open a WiFi scanner sometime. Unless you're living way out in the country, the 2.4GHz spectrum will be pretty much full. Everyone has a 2.4GHz router and you're likely to get a lot of interference.

Really it's the same reason computers moved to 5GHz, and now 6GHz.

Yes and no, depending on the environment. In an apartment building, the wall penetration is a liability, as the 2.4ghz spectrum, with only three channels, gets extremely congested. Going 5ghz helps immensely, with more channels available and less penetration, so you get more spectrum reuse.