Hello friend. I asked to myself the same question as you, many years ago. Then I learned that studying calculus and mathematics (I studied, five courses of mathematics and four physical) allows you to prepare your attitude for the resolution of complex problems. In my view, it is a kind of prior training, as the athlete begins training with jogging or the singer performs exercises to prepare her voice.
Secondly, there is sometimes specific knowledge not offered at the university that you will need when you're at work. You may need to get a book and learn it yourself. Sometimes that knowledge is based on physics or math, and if you don't have a base it will prove difficult to handle and understand.
Finally, engineering has many branches. So for example the area of maintenance is very operational and may not require math every day, but if you are working in academics and research you will probably need to use mathematics and physics regularly. In this sense I think it is necessary and indispensable to academic training for engineering.
In closing, particularly in my work, I do quality measurements of electric energy. I use measurement equipment that analyzes electrical current waveforms and voltage. The analysis uses computers and requires comprehensive and complex calculations. Although I use the computers and don't generally calculate myself, as an engineer I must know the process. I also used calculus many years after graduation, during my graduate studies.
I hope I have been helpful to your concerns