I want my IoT to work off-line with no talking to the Internet unless I explicitly let it for some reason. I want it to interoperate with other things and not just some shitty app on my phone - I don't carry my phone with me around the house all the time and it's a PITA anyway.
I could go the DIY route and bust out the soldering iron and some ESPHome compatible chips, but that's not my passion and life is too bloody short. And even if I did I'd still have strong reservations doing DIY around the 240V AC mains power.
¹ That, and the first thing I'd automate is light switches², but the regulations around mains power wiring in Australia are pretty stringent and the only AES certified IoT light switches I've seen look like I would have and adversarial relationship with and can only be controlled by a shitty app.
² Automating light bulbs themselves is a sub-optimal solution in most circumstances, in my opinion. Perhaps if I wanted to control the colour, but not for on, off and brightness. If I did that it would just make me feel sad.