Why does my receiving address keep changing?

A hierarchical deterministic (HD) wallet, like Edge, generates a new receiving address within your wallet every time funds are received into an address. All addresses from that same wallet can continue to receive funds even though the address has changed.

The address automatically changes to provide increased privacy and security so that no one will easily be able to find out the total balance of an account by simply looking up a single address.  It is important to note that Ethereum addresses do not change for every transaction, as individual ERC-20 tokens need to be tied to a specific address which contains ETH in order to be sent out of that particular wallet.