[Antilochos]

That last sentence; it still keeps me puzzled why Verstappen signed for such a long period. He could of choose any team he liked I believe.
Unless, he agreed a clause that if car cq. engine is not compatible for championship, he can walk. Horner nor Verstappen will ever tell you early of this clause.

For Ricciardo, I'm not so sure he has as many options as Verstappen. Not saying Verstappen is that much better, but Verstappen has a exponential grow curve ánd is very young. Great combo for teams. As a bonus, he already is a star.
Ricciardo on the other hand is very reliable, fast and also a star. But he reached his peak already (or there is not much grow left) and is moving into the autumn of his career (at least I think that). Yes, he might be able to catch a championship, but Verstappen has the potential for a team to catch multiple championships.
In short, Verstappen is long term investment and Ricciardo short term (in team perspective). With Vettel and Hamilton already there, a short term investment might not be worth it for the teams.

Option for Ricciardo; early retirement (out of F1) of Alonso and Renault engine becomes better, McLaren could be a team for him.
Vettel in Ferrari, Hamilton in Mercedes, Verstappen in Red Bull and Riccardo in McLaren. Would love a fight for championship like this.

I think this is a bit harsh on Dan Ric to be honest Anti. I think he is a class act and has better / more mature race craft than Verstappen (at the moment). Don't get me wrong, I'm a big Verstappen fan and I do believe he will be WDC sooner rather than later. I also love watching him drive. But, he is still a little bit green in my opinion and will get better as the seasons go by. Blistering fast, but not as good race craft as the likes of Danny Ric or Hamilton (yet).

I think we agree. I like Ricciardo a lot. As a person my favourite driver on the grid even. As a driver I think he is up there with the best (therefor my wishful thinking of a fight between Hamilton, Vettel, Verstappen and Ricciardo - consider all four could win a championship with evenly matched cars).
All I'm saying is that from a team perspective, at this certain moment in time, Verstappen is a more interesting deal. You get a young driver wich is already very good, but could be extremely good. A new Schumacher era for a team in prospectus. 
With Ricciardo, you get a very good driver also, a bit more mature and reliable even. But, looking at statistics (not of Riccardo specificly, just how people and athletes develop), he will not become more than he is. Why, if you are Mercedes or Ferrari, invest in a driver that is more or less equal to a driver you already have? Vettel and Hamilton will leave before Ricciardo does, but not that much time between them.
Long term investment. You got Verstappen, Ocon, Saintz, etc. Not the honey badger I'm afraid.