After spending some time adding info to OSM, you'll start to see plenty of cases where Google and Yelp have info for an establishment that's nowhere to be found

After spending some time adding info to OSM, you'll start to see plenty of cases where Google and Yelp have info for an establishment that's nowhere to be found on their website. And even for some businesses that don't have a website at all. Some of it's extracted from their street view imagery, but some of it clearly isn't. I can walk by my local bakery and their phone number and hours aren't posted anywhere visible. Maybe they're on the takeout menu. Maybe a business card. Maybe they're printed on the receipt. Maybe you actually have to ask someone. You can't assume that everything on Google Maps is from scanning public web sites. Sometimes, apparently, they do some actual investigation. Plus, Google's not always right anyway! Nothing's more embarrassing than being caught copying incorrect information. So do your own research. Obviously copying info from a public website is fine, but info on the ground is going to be more complete and reliable. (Plenty of businesses are sloppy about updating their websites.)