Virtually everything in a modern development stack contributes to the problem. Buses are optimized for bandwidth at the cost of latency. CPUs are broadly optimized for throughput at the cost of latency. OS design is optimized for throughput and isolation, again at the cost of latency. Language runtimes are optimized for feature-richness, again at the cost of performance. Languages are optimized for quality of life features that carry hidden performance costs, like virtual functions and exception-based control flow. Developers compound this with dozens of layers of indirection and abstraction until finally, eventually there's a message on screen for the user.

There isn't a singular cause to brainstorm. It's everything in the entire stack optimizing just a bit in other directions that produces the end result of disappointing, sluggish computers despite their actual capabilities. This discussion isn't going to tread any new ground either. All of these things are known because there are people who can't afford modern computing, like the HFT firms that are all on FPGAs now and real-time embedded systems. It's not hard to do, it's just tedious and expensive the way development used to be for everyone.