That may be the case for live viewing, but those that record longer term generally do it to a server out there. I have some from a company called Yi that I now refuse to use: they used to support local recording to SD card instead but that broke and the support answer seems to be “use the remote recording”, the remote recording only supports a short time window unless you pay a subscription, and they started flooding the ap with adverts if you don't pay for the sub in any case. The streams are non-standard so the cameras require custom firmware to make work with open source solutions, so I've just bought some better cameras that are said to work out of the box. Now I just need to get around to setting them up…
Cheap Chinese IP Cameras: never again.