I was wondering the same thing myself about taking probiotics for Crohn's Disease. I had been taking one a day for several years and honestly never noticed much difference with it. I was just about to try looking into other brands and I did some research first. What I found were several research articles that found that probiotics were not helpful for people with Crohn's, and that in fact there was one study where taking daily probiotics caused an increase in negative symptoms.
They said that since this is an autoimmune issue that the body sees any bacteria, good or bad, as a threat and will tend to over-react in fighting it off. However, if you eat foods that have probiotics, or if you consume prebiotics which just feed the already occuring good bacteria in your gut, then you are more likely to see positive results.
I recently purchased some chicory root tea, a prebiotic, and I'm going to see how this goes for me.
Of course, with all of this stuff, everyone is different so it's worth a try to see how it goes for you. Some people may see a benefit, I personally did not.
Good luck!
