Why people wear jackets while exercising?

Question

In gyms, i see people wearing jackets and jogging pants.. but some people wear sleeveless and shorts. is it something to do with the room temperature or something?

Answer 1

usually its because it make you sweat more. and the more you sweat the more weight you loose, the faster your heart rate goes and the harder you work.

Answer 2

so that they sweat more and lose wight faster

Answer 3

so that they sweat more hence the name "sweat suit"