Yahoo controls 8% of search traffic and costs $4bn. Google controls 64% of search traffic and costs $558bn. That's a 17-fold difference in the price for 1% of the traffic. Even more if you take US search traffic only (to exclude Yahoo Japan). Verizon can get rid of the costly parts of Yahoo (mostly its media business) and have its own small Google to make cash. That was $1.8bn per year in 2015, while Yahoo's overall…
And mail would be just fine if they'd remove all the crap so it would run faster.
Lots of non techy still uses yahoo mail, and that won't change as long as the service exists.