Two of my former employers (entirely different companies) gave admin rights to the technicians, who were allowed to install any software that didn't require a license fee, so I could install TCC/LE ver.13. In both cases, I was not allowed to install commercial versions of Take Command or TCC, even if I paid for them out-of-pocket.
Therefore, my main expertise with Take Command is with its batch scripting features, not with the GUI features of the full product. So I would keep two versions of Take Command at home (one current plus TCC/LE) and use TCC/LE at work. Most of the time, I made sure that any batch files or scripts I wrote would run under both versions. That also explains why most of my TCC scripts use sed, awk, or some free GNU utilities rather than TPIPE.
So to answer the original question, one reason to keep two versions is to coordinate batch files that you write and update both at work and at home.