Don't think there is any reason not to take them (yogurt tastes good) but I also don't think they do a lot of good. Compared to the number of bacteria (100 trillion) already in the intestines, the amount of bacteria in yogurt or pills is very small. Some diseases can benefit from a bacterial infusion, C Difficile is one, but you need to get a lot of bacteria to be really effective.
Antibiotics can upset the normal gut bacteria balance and probiotics might help there.
One bacterial transfer that is effective with C. Difficile is a fecal bacterial transplant. Yup, there is a certain "iiccckk" factor but it does work.
https://en.wikipedia.org/wiki/Fecal_bacteriotherapyDon't want to start a debate, to each his own.
Jim