Correct me if I am wrong but why can't you get,

[ethan]

say a 12.5 kg olympic weight or a 7.5 Kg olympic weight etc?

 

[ethan]

because we have 2.5kg , 5kg and 10kg plates so no need for them.

They are available for the standard 1 inch fitting.

 

[ethan]

It would be a waste of space.

It's actually the opposite on the standard 1inch format. 12.5kg alleviates the need to add a 2.5 kg, thus saving space.