There are a lot of users who use the Bitcoin core wallet.
For a fully verified node，they face a huge problem, that is, more and more hard disk space. up to now（2018）, more than 200G space is required. cpu and memory，it is continuous consumption and will recover after use，however, the hard disk space is a hard requirement and cannot be released after being occupied.
The beginning of Bitcoin, 2009--2012，the hard disk space less than 1G,
in 2015, 20G space is required for a full node.
now, more than 200G.
so, follow this, more and more nodes can only be simple payment verification nodes. Machines running full nodes are concentrated in the hands of large disk users, like a mining pool and ASIC, contrary to decentralization, will also become a security risk for Bitcoin.
Think about it - what was the size of your hard disk 10 years ago, when Bitcoin started and what is it now. Most people would have had 128GB or 256GB hard disks at that point, while now disk capacities are measured in TB. Technology is advancing quickly. Otherwise, people can prune the blockchain and continue using Bitcoin Core; else they can switch to light wallets.