Why in general has RAM been so limited in computers for such a long time? A decade ago we were expecting new kinds of RAM to replace hard disks entirely, using

Why in general has RAM been so limited in computers for such a long time? A decade ago we were expecting new kinds of RAM to replace hard disks entirely, using new computer architectures that did not use disk drives at all. Instead most general use computers have been stuck with 8GB or 16GB of RAM for like a decade. A few go up to 128GB. It seems like RAM has been artificially limited as a sales feature (price tied to RAM size as a feature customers easily understand similar to CPU speed), which has limited greater use of it. Also similar to the way the size of SD cards that can be handled in devices are never future compatible (got a new 1TB card? Good luck using it in your older phone!) Perhaps there are national security reasons for this? Like a computer that has 10TB of RAM could simulate nuclear bomb reactions to a degree of fidelity and with a speed that would give adversaries new capabilities? I don't know, but I know it seems like an artificial limitation. Possibly there are hardware limitations (like more RAM uses more power, but RAM could be turned on and off and speed managed just like CPU's are, depending on dynamic need). CPU's are currently limited by the I/O speed of data, so moving all data to RAM could bring huge performance benefits, yet current computers are still very much limited by RAM sizes and RAM-CPU integration.