Are somehow worthy the golden pantaloons ?
If they are only a non usable item, why do I have to identify them ?

You should identify the golden pantaloons to make sure to get some XP for them.
There is also a QUEST with them:

****** SPOIL ******

Normally, you are meant to take the pantaloons, identify them, and hand them back to their owner and get some XP. Later in the game, you'll meet Mr Shade in 'The Splurging Sturgeon' and you can talk to him for hours but it will never ever amount to anything.
OR:
You take them along with you, all the way to the city of Baldur's Gate. There, in a tavern called 'The Splurging Sturgeon', you'll meet Mr Shade. You'll talk rubbish to him for a while until: He'll tell you he was meant to meet the rightful owner of the pantaloons and that you're not the one, and he'll call you a thief and tell you you won't get any XP for that, and he'll snatch the pantaloons from you and dash off.
- weird easteregg, isn't it?!

How can you know such things ????
Are you the Baldur´s designer or what ????

Nah, unfortunately not.
I've been playing the game for a really really loooooooooooooooooooooooooooooooooooooong time and all I've explored so far is the ways of good players. For about a month now, I've been playing a neutral setup, and once I've finished, I'll try the evil alignment. What keeps me going back to the game over and over again is that everytime I play there are new aspects to it.
Example: Having Jaheira in your party or not determines how the druids in Cloakwood react towards you.

PS: I do have an army of veteran Moggls...

spoiler

ive heard that you can get a great armor from em
just keep em in yuorbagpack and import your saved game into
bg2 there you can somehow find golden shirt and then import to
bg2 ToB there you can find like golden-something after that you can go to someone and that someone puts it topgheter into a armor
/i dont know if its true thought

I heard that if you had the pantaloons in BGII then you could met the gut that gave them to you. According to my 2nd cousin he says that they're dirtier than when he gave them to you.

SPOILER

If you import your character into BG2 and he has the pantloons on him you'll find them in irenicus' dungeon. Then later on you can ransom a women in exchange for some silver ones. And in ToB there are some people that you ask to get a beholder eye stalk and they'll give you bronze pantalets aswell. You bring these to a knome on the balthazar's city and he'll combine them into an armour that has custom weapons on it. It also turns your chacacter's paper doll into an iron golem

Spoiler

A very very very powerful Golem that tends to decomate everythin gin it's path.

http://www.gamebanshee.com/baldursga...oonsenigma.php

Click for the truth behind the pantaloons. ;)