Why does Electrum keep creating receiving addresses?
Electrum allow you to create HD wallets that use seed to generate a near infinite amount of addresses.
All bitcoin addresses are public so it is better to use different addresses each time you receive coins for privacy reasons
Here is the official answer to your question from electrum: https://bitcoinelectrum.com/frequently-asked-questions/#why-does-electrum-give-me-a-different-address-everytime