Although I'm not new to the fact that all transaction have to be spent in a single output buy why does it have to work that way??
You can send all amount in your chosen inputs to one output or some outputs include your change address.
For privacy reason, the common advice is don't send round number, don't send all inputs to one output and try to use change addresses.
- https://bitcointalksearch.org/topic/what-is-the-change-address-on-bitcoin-wallet-read-to-know-5190841
- Blockchair.com's General guidelines for sending BTC transactions
- Don't send round amounts. Instead of sending 0.1 BTC, send 0.10125
Use Bitcoin Mixers
- Mixers add an additional layer of privacy to a transaction to avoid exposing user identities.
Avoid reusing wallets
- Don't send your Bitcoin change to the same address you use for sending bitcoins.
Avoid including many of your addresses in one transaction
- Any time you can, try not to send BTC from your various Bitcoin addresses.
Avoid using "send everything" option
- If you are withdrawing funds from an exchange, it is okay.
- If you're moving funds to another wallet, do not transfer the whole amount to another address. It greatly compromises your privacy.