Why do some denominations not wash feet before taking communion? Why is it that some denominations follow the ordinance of humility as described in John 13 while others do not? What reason is there for not performing the foot washing ceremony before partaking in the Lord's Supper?
While I am not familiar with any denomination that practices footwashing as part of communion celebrations, I can address an issue that is implicit in the questions.

Descriptive is not the same a prescriptive

In other words, just because the Bible describes some people as doing something that doesn't mean all Christians should always do that too. As an extreme example the Bible tells us of bad things done, even by people described as 'righteous, such as the adultery of King David, and Peter's denial of Jesus. We are not expected to follow their examples. We have to use judgement, and follow Biblical guidelines, as to what is an example to be followed and what is description.

The Lord's Supper itself is not just descriptive. As well as describing what happens, Jesus' command is recorded: "Do this as often as you eat/drink it". No such command is attached to washing the disciples feet. In fact Jesus makes it pretty clear that what he is doing is not actually about feet, but about leadership and humility. Jesus expects leaders to act with humility towards their followers and be their servants. Actual literal footwashing may or may not be involved. Most Christians would say that a leader who carried out literally the act of washing people's feet, but behaved arrogantly towards the people they lead was not carrying out Jesus wishes.