Because that is good advice for want of a better workaround. You act like that is a huge burden, it's typically very easy to do! Searching for a model number and 'manual' will get you to a manual, most manuals are very short and quick to parse especially if all you are looking for is 'will this require an app' or similar.

So, yeah, it is good advice if the outcome is important to you and you dont know a better way to protect yourself from accidentally buying something like that. Unless you know a better way and are holding out on everyone?

I regularly download the manual prior to making large purchase, such as appliances, home control systems, etc. Checking out the app itself is good too.

For printers, I also recommend pricing out five years of supplies. I bought a printer that cost 5x as much as one with similar specs, but ends up costing less in supplies.