People look at is as an advantage AND a disadvantage for the following reasons. They think it's a disadvantage because parents are required to pay for the uniforms, which usually consist of a few pair of pants, a few shirts, possibly both long sleeved and short sleeved. The initial cost of this can be high, especially if parents have more than one student that they need to clothe in a uniform.
It's looked at as an advantage because parents only have to buy the students their uniforms. They can cut back on the other clothing that the student has because they'll mainly be wearing the uniform so the need for extra clothing is smaller than if they had to wear different outfits to school all of the time. Parents don't have to worry about buying their children "designer" clothing to fit it. Some parents will donate, or pass on, their children's uniforms once they outgrow or don't need them anymore, so that's another advantage, cost wise.