There are two common reasons for multiple routers
One (As he said) is because it's too far from Router one to the other end of the house.. I've had to use "Extenders" in the past in some cases.
Two: IN my case one router is a 2.4GIG. the other is.. I think a Dual band (though I'm nto sure it may be a 5 only POS Spectrum router) and some of the hardware here only connects at 2.4
One option I did not include.
This setup
Modem----Router 1 (Router)--------- Router 2 in Access Point mode
In this set up router 2 is just a wi-fi access point it does not "Route" it does not assign IP addresses. it is simply an "extension" of router #1 (--- is cat 5 cable) I'm not sure if Router 2 (Access point) has it's own SSID/PSK or not in this configure as I don't use it. But I may give it a try as it would solve an issue for me.