Sending value is only one reason to use BTC, it might even be the main reason. However, BTC is a ledger for posting vbytes on the timechain. That's all. Those vbytes can represent locking and unlocking scripts to "send" sats. But those vbytes can also be used to establish payment channels (Lightning Network), "anchor" data from altcoin chains (Liquid Network), put messages in blocks ("Chancellor on the brink..."), host JPEGs of 8-bit monkeys (Ordinal Transcriptions), or JSON objects that represent token transfers (BRC20) or even keeping botnets online. You can even use up a ton of vbytes doing wallet maintenance (UTXO consolidation a.k.a. self-transfers) or doing fancy script 'programming' onchain with miniscript. It also cost exactly the same to send 1,000 sats onchain as it does to send 1,000 BTC (assuming it's just one UTXO input, single sig). Therefore, every use of a vbyte does not necessarily correlate to any value changing hands. It certainly does not matter how you choose to denote that value (USD exchange rate).
As for the addresses: unique addresses do not identify unique users. A user can have many addresses. Further, a single address might be shared by many users (in a custodial or multisignature relationship).
Since the following are true:
  • fees are measured in sats/vbyte
  • addresses are not 1:1 with users
  • vbytes are not 1:1 with value transferred follows that USD transaction volume and new address use can decrease while fees remain flat.