Why is it so that a high rise project adds 5 stars to an MEP company's prequalification..?

The basic reason is that as one goes high up , providing MEP services become more and more challenging.
Whether it is power, ventilation, HVAC and plumbing.
Having done a high rise adds strength to company's capability and hence a special preference.
Hope this clarifies.
Narayan G Mukhopadhyay