Today, blocks are distributed fast enough. If we scale to 10k TPS, blocks will need to be about 2 GB, right? Then it will take non-trivial time to transmit blocks over slowish links. That would put miners/pools based in countries with shitty internet connections at a disadvantage.
Miners can ensure that their peers know in advance about the txs they're mining. Then only the first few bytes of the txids would be necessary to uniquely identify them, and this is all that would need to be broadcast in bursts when blocks are found. Broadcasting the first say 5 bytes of the txid, instead of the full ~350 byte transaction, means a 98.6% reduction in necessary bandwidth. So 2GB -> 29MB.