They broadcast Wi-Fi signals, switch network traffic, and translate Internet packets. The one thing these devices don't do - route. Residential Gateways, those things that most of the world calls routers, have lots of problems.
Almost all Residential Gateways on the consumer market have known exploitable security weaknesses. They're made for simplicity, not security; setting up, not staying up.
Most of these devices have less powerful hardware than what is in your phone. Residential gateway manufacturers put the bare minimum inside their products to cut costs, but end up cutting performance.
They may not be routers, but Residential Gateways do almost everything else. Their makers try to put an entire network infrastructre into a little box, hoping it all works well enough. Centeralization is good in some places, but never when it is all dependent on cheap a residental gateway device.
More information about network services coming soon