Before the PC, computers were devices: custom hardware combined with software specifically written for the machine, and the machines themselves were usually designed for a select few (if not single) purposes. The problem that PCs seemed to address was diversity. Where customers had previously relied on one company to support both hardware and software, the PC clones opened the doors to a brave new world where anyone could build, support, or maintain a computer.
It was a revolution that made computers affordable enough for anyone to own, for any business to adopt, and allowed countless entrepreneurs and skilled technicians to find work for themselves: outside the confines of long established corporate hierarchies. Unfortunately, the open source software revolution took much longer.