4TB is a huge amount of data. And it’s costly to keep data spinning. 4TB storage an in apple device is going to set you back a lot of money for example. Not everyone has a NAS or the ability to run one and even more importantly to back it up effectively. It becomes a large monkey on your back and a cost and not an advantage.
Looking at my device storage, I have 91Gb online for 5 people. That’s everything we have ever done. Because we care enough to look after it and curate it.