They’re being coquettish and hope their dainty ankles have caught your eye?
;)
Maybe. or...
In those days it was common practice that people trailed their garments out of pride and pomposity.
So the Prophet said: Anyone who wears his garment below the ankle, out of pride, will enter hell. Only the humble will enter heaven. It’s in the same line with the hadith that says: Anyone who has the weight of a mustard seed of pride will not enter paradise
In another tradition the Prophet defined Pride as “Denouncing and Denying the Truth and despising People”.
The keyword here is pride. If you see any Muslim wearing a “short trouser” it’s because he wants to copy the Prophet who himself shunned trailing garments. But the caution is even if you wear “short trousers” but still have pride you will be punished by God. Pride can be exhibited in several ways (not only in the way we dress), so it’s incumbent that we watch our hearts and train ourselves in humility.
I cannot remember the exact verse, but the Bible also mentioned the arrogant attitudes of the Pharisees how they loved wearing trailing garments and being followed by people.