No, the physical symbols are not absolutely necessary. For many people, yes. That is why Jesus told us to do these things in his remembrance. Many people understand and remember ideas better when they have not just words, but also actions in which they participate. The lesson is being made in more than one way, and can be communicated to a wider variety of people.
Some people think well in abstract thoughts, in the world of ideas.
The Old Testament had many rituals that were physical signs and symbols of spiritual truths. God knows that humans often need such visual aids. Some people will find it helpful to participate in the Lord's Supper more often than others will. Many WCG members used to be in churches that observed communion weekly, and for some of them, the bread and wine was a ritual that had little meaning. The focus was on the ritual, not on Christ.