Google relies on ads as its major revenue source. In fact, 88 percent of Google revenue comes from advertisement.
Showing ads is the way of doing marketing. It has been one of the major marketing act since long time.
Previously, to advertise a product, companies use to hang posters/banners around on the roads or show ads on television.
Now, in the present era they do it digitally through Google, Facebook, Youtube, Snapchat and so on.
But, What if the advertisement strategy changed again? What if the product doesn't become profitable throgh digital advertisement in upcoming year and they switched their strategy?
Who knows what type of advertising platform comes in future?
And, also not to forget about Ad Blocker, which is growing rapidly. As, Ads are annoying for end users, almost every body wants to put ad blocker on their device.
The Nokia which had billion+ users failed in preety same way when newer smartphones like iPhone entered the market. (See the picture below)
The failure of Yahoo! can be taken as another example.
The change in technology happens so frequently that no one can predict what might happen in coming days.
The product that we rely on today could be of no use tomorrow because there might be a newer substitute to that.