I'm wondering why Monero requires "synchronization" while Bitcoin doesn't? I'm asking only about the case when a remote node is used, because it's obvious that local blockchain will require synchronization. In the case with Bitcoin (for example electrum wallet), I can open the wallet after a month of inactivity and it will be ready to use almost immediately, unlike with Monero, which requires about an hour to synchronize.
Thanks!
Why does Monero require synchronization, but Bitcoin doesn't?
If you want to run a Bitcoin full node you still have to synchronize the blockchain and if you have a wallet loaded it still needs to scan the blockchain.
...(for example electrum wallet)
An Electrum wallet is not a full node, hence this is a poor comparison. If you want an Electrum like experience, Monero has comparable light wallet implementations.