Firstly, because it's awful.
But more importantly, given that it only recently gained a university and doesn't have a cathedral (as far as I know) it can't be elected onto the register of cities.
There are some places, for example, Guildford in Surrey or Reading in Berkshire that satisfy both requirements but yet have not been elected onto the register.
Huddersfield does not have city status in the UK because it has not been granted a royal charter to be recognized as a city. City status is a ceremonial designation given by the British monarch, and Huddersfield has not met the criteria to receive this status.
The city of Huddersfield in located in the United Kingdom. It is part of the county of West Yorkshire. Huddersfield lies halfway between Leeds, also part of West Yorkshire and Manchester, which is in the county of Lancashire.
Huddersfield Town
Huddersfield is in the Metropolitan Borough of Kirklees, in West Yorkshire, England, halfway between Leeds and Manchester. It lies 190 miles north of London, and 10.3 miles south of Bradford, the nearest city.
Huddersfield Town, Hull City, Norwich. that I am aware of.
Northampton Town, Leeds City, Huddersfield Town and Arsenal
Huddersfield, check it if you don't believe me
Huddersfield's population is 146,234.
It used to be at one time, but I think others may have surpassed it in size in recent years
Per 2011 census population of Huddersfield is 162,949
University of Huddersfield was created in 1825.
Huddersfield Giants was created in 1864.