Which they do, if you access them using a non-Chrome browser, or at least used to... I confess I'm not sure because I still use Chrome. I agree with you about the advantage of "if you're already using it, something has to be a LOT better to get you to switch".
And also on gmail, googlemaps and YouTube… They even paid for ads in the subway here in Paris! They also bundled it with software like Adobe Flash, which made it available on virtually every computer circa 2010…
And they ship it as their default browser on Android…
This is probably just me, but whenever I see an advert for a web service on TV or on a billboard (especially for stalwarts like Google or Ebay), I always apply the same logic: their product must be crap if they're having to advertise it the old-fashioned way — it feels desperate and demeaning to the product.
GSuite pages constant suggest downloading Chrome.
2019 Google has a lot of ads for Google.
It's not the default browser on most Android phones sold. Samsung Internet is.
Android has more than 80% of the smartphone market and Samsung has around 20% of the whole market, which makes 25% of the android market.