Or don't actually benefit from being connected devices.
The 5,000 number sounds impressive but what does it mean? How many devices realistically can one household have and benefit from. Reminds me of Android in their land grab days, fragmentation city. Lets get as many irrelevant connected devices as possible never mind what they are!
Its means flexibility. You are restricted to a small subset of devices that HomeKit supports, and some of those too are junk.