Okay, you are making a significant logical leap from ‘players do not know about tools’ to ‘if players knew about the tools from day 1, they would be more likely to stay’. The tools being in-game might make a difference for a tiny percentage of players who would otherwise leave - but most players who leave do so because EVE wasn’t the game for them in the first place.
Again, simply putting the tools in the game doesn’t make them more functionally usable to players - not only do you have to find them in the already large menu of tools, you also have to explain what the tool is and how to use it (and can I tell you how many vets I have spoken to who didn’t know about the Compare tool and how to use it?). Unless each and every tool is given an in-game tutorial, the tools are just as inaccessible to a new player in-game as via a third party site. The only argument for in-game is not having to open up a website or app separate from EVE to run them - but that is countered by app developers not being locked into CCP’s development cycle and thus being free to iterate on their work as needed instead of only when CCP budgets for QoL improvements.