[pietjepuk88]

When syncing, you can choose to either build and save the state for every block ("archive" mode), or save only the latest state ("fast" mode). The former requires quite a bit more data than the latter (currently 500 GB vs 32 GB for the Geth client) [0]. The default for most contemporary clients is "fast" mode.

Note that with the "fast" mode you still have all the blocks, and with that all the information needed to recreate the state at a certain block somewhere in the past. And you can still help the network by syncing those blocks to newly spawned archive or fast nodes. It's just that requesting the state (e.g. balance) at a certain block in the past takes some computational work. Most people are not interested in that however, which is why it's the default synchronization mode.

[0] https://etherscan.io/chart/chaindatasizefull vs https://etherscan.io/chart2/chaindatasizefast