To me, it's maybe because the verb "to please" in English. This would mean, 'The pants please.... and would need something to please. eg: "The boy pleases his mother". Obviously this is not the case in German.
"The pants please the customer." I can see now it's a totally different thing.
Just picture a fellow in a clothing store. He's just tried on a pair of pants and a couple of shirts. The person assisting him asks if he found something he liked (i.e. that he wants to take to the register to purchase), and he replies "The pants, please." Then he's handed the pants.
Wataya wrote it already in this discussion. "Hosen" is the plural of "Hose". The singular word of pants/trousers is called "Hose" and covers both legs.
The short swimming pants for sports like the Olympic Games are called "Badehose". One "Badehose" covers all the relevant parts.
Please, put the comma before "bitte" and make the German sentence great again.