There isn't an official reason available publicly for why Aligarh Muslim University (AMU) doesn't offer a Bachelor of Design (B.Des) program. It could be due to various factors like:

AMU might prioritize other academic disciplines and not have the resources to establish a full-fledged design program.

There might not be enough student demand for a B.Des program to justify the investment in faculty and infrastructure.

AMU's Bachelor of Vocation (B.Voc) program in Fashion Design & Garment Technology could be their way of catering to design aspirations while keeping resource allocation focused.

Diploma programs are known for their practical approach, equipping you with technical skills like pattern making, draping, and garment construction. These programs are often designed in collaboration with industry experts, ensuring the curriculum reflects current design trends and industry needs.

https://design.careers360.com/download/ebooks/know-all-about-fashion-design

I hope it helps!