My guess is that the WiFi networks around me are constantly swapping bands in an attempt to find an empty one. From memory, there are only about 14 bands available!!!
There are either 11 or 13 numbered channels, depending on what country you are in. However, the channel numbers were set before any of the WiFi standards now in use exist.
Present systems using the 2.4GHz band each take a frequency range of either four or eight of the old channels.
When 11g was the fastest system a few years back, careful arrangement could allow three or four systems to coexist using channels 1 - 6 - 11 or 1 - 5 - 9 - 13.
Newer, faster systems often take a block of eight or nine channels. There is no coexistence, only interference and "hidden station" effects.
And that's not counting all the other non-WiFi stuff that uses the same 2.4GHz band, anything from bluetooth to model radio control to video senders, wireless CCTV and video baby monitors etc., that do not register on WiFi receivers but still "jam" other signals.
For me, any place selling fixed devices such as PCs & smart TVs and saying they are suitable for WiFi ought to prosecuted.
And promoting WiFi for home automation devices etc. should be a crime.
There are other dedicated bands and systems for automation such as Z-Wave & Zigbee etc. that have no impact on WiFi and are not affected by interference from other WiFi systems.
>/rant<
(And yes, all my fixed ethernet gear and security is hard wired and automation is either wired or Z-Wave. I do practice what I preach).