Why is there sometimes no output that sends funds back to the sender's address?

Question

'A' has one bitcoin. 'A' tries to send a 0.5 bit coin to 'B'.

Two utxo are created.

First, "utxo" sends "B" 0.5 bitcoin. Second, "utxo" where "A" remits remaining bitcoins to "A" except for 0.5 bitcoins and fees.

utxo 1) A-->B

utxo 2) A-->A

The url below is the URL to see how UTXO is reflected in the Bitcoin block detector. https://www.blockchain.com/ko/btc/address/1JK1MAseF6TRjBidxz45T1VnYVFummCTBZ?offset=5250&filter=6

https://www.blockchain.com/ko/btc/address/17YVBuR8oCaC78xQtWbx1gkfmhjt52UMK7

https://www.blockchain.com/ko/btc/address/1HpyyzMwq1QZqS43guyy9GvLdc6jMWoy8z

Sometimes when you look at a block detector, there's some TX information that you don't understand.

For the following URL, the coin in the wallet is used to transfer the same bitcoin from several wallets to another.

There is also a "TX" that displays only the amount of coins received from one wallet.

In the case of the url below, I transfer Coin from my wallet "13E3dBUWUHV8XpgJib795yqRTmyX47jWMk" and there is no utxo sent to my wallet.

utxo 1) A---->B

utxo 2) A---->C

If this is how the money is transferred, can we know why this is happening?

https://www.blockchain.com/ko/btc/address/13E3dBUWUHV8XpgJib795yqRTmYX47jWMk

Answer 1

You are confusing addresses and UTXOs. What you are talking about are addresses, not UTXOs.

The inputs of a transaction have no effect on the outputs. There is no requirement that a transaction must have an output that corresponds to an address that is an input. In fact, what you described first is known as address reuse which is highly discouraged. The behavior you see in the address you have a question about is exactly the kind of behavior that is encouraged: the change is sent to a newly generated address.