One of the reasons why I do not like to go in a group with a guide is because there is little flexibility as to time. If you are part of a tour group, you are subject to their time schedule and time restrictions. For instance, imagine you are touring Paris and stop in at the Louvre Museum. The guide will usually take you to the more famous pieces of art and give you only moments to look around on your own. However, what if you want to take your time and look around for a while? That would be impossible because otherwise you will keep the bus full of other tourists waiting. There are other examples of these restrictions including how long you get to eat and what time you have to get up in the morning. Therefore, traveling on your own supplies more time flexibility.
Another downside to going on a group tour is that there is very little privacy. For example, imagine you are on your honeymoon, but you are traveling with a tour group. This is a very romantic time that a new couple would like to use for time with each other. However, in a group tour you are always with other people and cannot avoid spending time with the group. The group eats together, travels together and stays in the same hotels. The honeymooners get very little time for romantic dinners, taking walks together or doing other activities that honeymooners would like to do. For this reason, it would probably be better for honeymooners not to go on group tours.
In conclusion, though tour groups may be good for some travelers such as older people, I do not think