Why are telescopes built?

[glassnumbers]

I think a more relevant question is, what benefit is there to having ANOTHER telescope up there, and what is the environmental impact, if any, of having multiple telescopes up there? I remember reading about a telescope up there that was long ago put out of service, but they couldn't remove it due to an accumulation of hydraulic fluid that had to be dealt with first. Was that a fluke/failure of an older design, something that would not be repeated with newer, more modern telescopes?

Aloha