Today, a BTC transaction requires the payment of fees in order to be inserted into a block, confirmed and recorded on a blockchain. This was not always the case. The fees to be paid to miners are not theoretically necessary.
BTC transaction on LN
First of all, it is not always necessary to register BTC transaction on BTC blockchain. Initially it was, but since the release of Lightning Network, transactions can be performed outside the chain, they do not require registration on the blockchain.
It is still necessary to pay a fee, but this fee will not go to miners who record transactions only on the blockchain, but to the LN node you use. For example, if you use your own node, you do not have to pay any fees or you can pay fees to yourself.
LN transaction fees are also negligible and therefore not problematic.
In fact, it is more interesting to focus on
The first transaction ever recorded on a BTC blockchain with BTCs sent from one user to another, included in block 170 on January 12, 2009, was free of charge. This means that the miner who mined this block, probably Satoshi Nakamoto or Hal Finney, has agreed to put this transaction on the block he mined.
Each block is limited in size and can only include a certain number of transactions, barely more than 3,000. When more than 3,000 transactions await a blockchain, miners choose the ones with the highest fees to include in the block.
This is why zero-fee BTC transactions have long been very unlikely to be mined by blockers who clearly prefer those with higher fees. Even today, some are sometimes included in the blockchain, but only when the queue of pending transactions is really very small.
The BTC network is overloaded
In the most congested periods in the BTC network, zero-fee transactions have virtually no chance of confirmation, and after some time, they are simply discarded and effectively canceled before they even pass. In quieter times, however, a few will be confirmed after a while of waiting, although the wait may take days, weeks or months.
It is worth remembering that for some private wallets, it is possible to either change the fees for a transaction that has yet to be recorded on the blockchain or cancel it before it is finally inserted into the block.
When the reward for the blocker is reset to zero, the only income for the miners will be the fees, so they are likely to have an incentive to confirm them only if the sender sets significant fees for them. However, it is possible that long before this happens, the block size may increase or the use of LN may expand to such an extent that the problem becomes unimportant.