[Hi!
As others have said, the decision to treat is very individual.
Keep in mind that the dmds have been around a very short time in the overall history of MS, So while we already know the possible outcomes of the untreated MS. we are just starting to get a picture of how the dmds are modifying the course.
Even Dr's admit that they are only 'moderately effective'. Does this mean that 100% of people might benefit ever-so-slightly, or that a much smaller group of people will get a large benefit?
The Figure 1 chart here is a powerful indication or treating vs nor treating.
http://www.drugs.com/pro/copaxone.html
Also since the current offerings are for treating RRMS only, it makes sense to me to try to keep it from progressing to a stage where no options to treat exist.
Good luck