It is, but it's a small one, typically both in cost and number. E.g. I have 5 led strips, half a dozen smart plugs, about 40 bulbs, and a dozen smart switches, and 5 smart radiator valves/thermostats. Replacing a bridge with Home Assistant and a 10 pound USB dongle isn't the problem if everything else speaks open protocols. As I said, I wouldn't object to requiring untethering ability even for those, but requiring open protocols for the other devices is more important.

Most of the above is Zigbee, which is open, but some is Tado and Lightwave, and if they go rogue it'd suck to replace the devices rather than just the hubs.