Basically, circuit switching implies that you are actually using a circuit through the global network to communicate. Whilst the older PSTN networks are more reliable than packet switched networks, they are more expensive to build and run. Packet switching on the other hand shares circuits between whoever needs them. A particular circuit could be carrying packets for several clients at a time. This basically makes it cheaper to build and run, which means cheaper internet access for all. It isn't as reliable, but before VoIP and video streaming, the reliability of PSTN networks wasn't really required, as retransmitting a lost packet doesn't affect the user experience in the same way (i.e. It may take a second or two longer to show you a web page if a few packets are lost. VoIP has challenges to solve to reach the reliability of PSTN networks due to packet loss. Losing a packet in a real time conversation can be noticeable, and retransmission is not always an option. There are some interesting packet interpolation methods). Packet switching is more appropriate for internet use as it allows several clients to share physical communication media, which in the long term makes the internet structure easier and cheaper to build, maintain and run. For the same reasons, packet switching networks are easier to scale than circuit switching networks.
