Why the industry insists on hiring full-stack developers?

I am going to write this in English because I think it is easier for anyone comment, so...

Today, after a coding dojo about react(which is really cool, but not my focus, since I am a back-end developer) I was thinking about why the industry insists on hiring full-stack developers. 

I do not think it is possible to be really good on both, front-end and back-end, I can understand the mindset of small companies about hiring someone who can write software top to end, but I can assure that you will not get the best of both worlds, so, almost every company, even the small ones usually have more than one developer on the team, so, why don't you just hire one front-end and one back-end developer. You are going to get the best of both world and also, people usually got more motivated working with they really likes(I think I never met a developer that do not prefer or back-end or front-end).

I will try to rest my case here.

If you are a front-end developer you need to be really good in:

Javascript, CSS, HTML, React, Angular, Node, Javascript frameworks in general, Web performance, UX, Package managers, Version Control Managers, and I could be missing something here.

If you want to be a really good back-end developer:

Few programming languages(Java, C#, Scala, Go, Python), TDD, BDD, Rest Services, SOA, Microservices, Relational DataBases(MySQL, SQL Server, Oracle), NoSQL DataBases(MongoDB, Cassandra, Redis), Search-Engine DataBases(Elastic Search, Fast), Unit Test Frameworks, Mock Frameworks, Version Control Managers and more.

Aside from technology standpoint, different mindsets are needed, it is very different to build a user interface and a service. You need to be careful about different things. You do not have to make your API beautiful or to provide the best user experience, but it has to provide the right data in the most efficient way. I think you've got my point here.

Now the simple math. Is it possible to have time for your social life and also dedicate yourself to be good on both worlds(I can assure you that 8 to 5 is not enough)? In my opinion, no. So, why people insists on hiring full-stack developers?

Leave your opinion, please!