As far as I can tell, it’s about quality of life, and switching skill sets wastes less off your time than returning to the sanctum and starting from wherever your alt left off.
For the least pain, the highest cost
I have 5 skill pages and now live off skill cleanse points, especially after the faming update. I have to hobble one skill set to sow and harvest, then change it back so I can still do the single task that skill set was setup for.
That annoyance, plus running back into my home beacon every time I want to do something different simply to change again, takes a fair chunk of my game play time. The limitations around character progression are the thing that come up again and again in every hour of play more than anything else.
Edit: That said, I recently wanted to reorder my skill pages. Since you can’t name them, you have to remember the purpose of each one, so I thought I’d reorder them to make it easier to remember… Until I realised it was going to cost 3200 cubits to achieve. I don’t know why I essentially have to go up 6 levels to “afford” the ability to reorganise skill pages, but there you have it