You do realize that all the crafting skills are not that many skill points? Whilst maxing mining takes more than 1000 skill points.
The current system encourages a degree of specialization - but not absolute. You can do without every skill, but some are very good for specific things (e.g. tool masteries), others are generally good but worse for specific things (e.g. power) and others unlock “special” things (like advanced crafting).
1 person with advanced crafting can supply a whole city. 1 person with maxed mining can’t. They’re trying to encourage us to spend more points into the end-game grind of our choice.
As for crafters being able to mine everything themselves - it might be true if you don’t sleep, but a maxed miner gets double drops from luck, twice the speed from agility, 50% less hits from power and can use better tools effectively due to hammer mastery. The same goes for hunting, etc.