You say this as if it is easy or inexpensive to do well... If it was why would the service even exist in the first place? Surely everyone would just do it thems

You say this as if it is easy or inexpensive to do well... If it was why would the service even exist in the first place? Surely everyone would just do it themselves. I also don't think you would be arguing that people bothered about WhatsApp or iOS tracking them should just create their own messaging app or mobile OS. The vast majority of software is not just difficult do yourself, but almost completely infeasible. In fact it's hard to even think of any software I use regularly which I as a experienced software engineer could easily build myself, let alone an average user concerned about this stuff...