Why am I constantly being asked to install apps

When I travel, as now, I often just bring my samsung android tablet, but much prefer the laptop. Curious, what is the reason that I so often get almost insistent requests to install the app, like for instance yahoo email. I am perfectly content with the regular version, but am asked all the time to install the app? Same is true for some other sites as well. There must be some type of financial motive on the part of the site offering/insisting on this download, I just wonder what it is? Is it because these apps all state that to install, they will have full access to your contacts, pictures, and I suppose credit cards and bank information as well! I get kind of sick of the privacy intrusion that these apps all seem to require!
Whatever happened to the days when you could just download a program, (app), use it as YOU like, and not have to agree to a bunch of BS to do so? Again, just curious!

 

it's called crapware! worse than viruses, they'll track you, every website you visit, send you spam, and steal your financial information. Any app which has bloatware in it, I remove it from my library and find alternatives or give up on it altogether