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.
Some have speculated that this action in the upper room was in response the the disciples argument (recorded in Luke) about who was to be the greatest in the Kingdom.
The task of washing feet was usually performed by the lowest ranking slave in a household. The task was necessary as anyone who has been in that part of the world prior to extensive use of motorized vehicles knows, donkeys leave manure wherever they go and they are used as the transport of choice in many small villages even today.
What Jesus did was less ceremonial than it was utilitarian. However, it could also have been done as a silent answer to the disciples dispute.
While several denominations have instituted foot washing as a ceremony (with or without communion), I do not think that the words of Jesus are meant to institute a specific ordinance or act symbolic of humility. I think that Jesus is saying that they should be willing to perform acts of service that are useful and necessary for each other without regard for how it would appear.
The "example" of Jesus is not one of ceremony, but of utility.
A parallel today might be if a bishop of a denomination was having a regular church member over to his house for dinner and the person had some dog manure stuck to his shoe. Instead of telling the person to take off his shoe and leave it outside, he asked the man to sit in a chair while he (the bishop) cleaned his shoe for him.