Why does the T-mobile app take up so much space?

I'm not quite sure what it's storing, I just know that a couple months ago I had only used about 60 GB ROM and now the usage has almost doubled thanks to the T-mobile app. I had no idea I could get rid of the app without rooting my phone. I'm just wondering if deleting the app might render my phone inoperable, like maybe it's necessary for basic functions. Thoughts?