Why "Idols" and Animals Are "Worshipped"
Now, being that I am a Pagan from a Christian upbringing, I obviously can't speak for EVERY religion when I answer this question. In fact, considering how diverse the Pagan beliefs can be, I honestly can't even speak for every Pagan.
However, from my own personal knowledge and beliefs, the worship of idols, animals, or other objects isn't worship of those things themselves. On just about every Pagan altar, including my own, there is a representation of the God and the Goddess, generally speaking. My Goddess representation is a Faerie Glen figurine that one of my very best friends gifted to me for my birthday several years ago and my God representation is a horse figurine that my big brother gave me for Christmas back when I was a teenager. They are not only very precious items to me, but through them I see the Divine.
Do I worship these items? No. No more than Christians worship the image of Christ on the cross. What these items serve is merely a representation of the bigger picture -- a focal point, if you will. We don't honestly expect these items to actually DO anything for us, answer our prayers, or anything else. It's merely a visual way we can connect with Deity.
People that seem to worship animals? While, as previously stated, I can't speak the same for them, I think that it might be the same for them, such as the people in India that revere cattle. Unlike here in America, cattle are treated with the utmost respect in India. They are not eaten, they are not abused in any form or fashion. They are allowed to roam pretty much wherever they wish, even right into peoples' homes which, if that happens, they consider themselves quite lucky indeed!
Egyptians also had animals that they revered in such a manner. Cats, for instance, were considered to be one of the most holy creatures in the world to them. They were considered to be representations as well as children of the cat goddess, Bast or Bastet. The Egyptians had other animal gods in their Pantheon such as Sekhmet the lion-headed goddess, Anubis the god of the Underworld that was presented in the form of a jackal, Thoth, who was portrayed as having the head of a bird call the Ibis, Horus, who had the head of a falcon. The list goes on.
I'm sure that those aren't the only cultures that have a deep reverence for animals to that point, but those were the two to come to the forefront of my thoughts where this topic is concerned.
To summarize: We, generally speaking, don't worship objects, animals, or other things. We just revere these things as representations of the Higher Powers, Deity, the Divine, or whatever else you want to call them. We see that Deity is in everything and sometimes it helps to be able to have that representation that we can actually see.
Think of it like this: While talking on the phone with someone is definitely better than not being able to talk with that person at all, it's still not quite the same as being able to talk to that person where we can actually see him/her.
It's the same with God and Goddess, or whatever deity you worship. Speaking to them without actually getting to "look" at them is like talking to that person on the phone. It's still comforting but not as personal. However, praying to and talking to God and Goddess feels a lot more personal and meaningful when we feel like, in some semblance, that we are able to speak with them "face to face". That's all it is. It's not worshiping the item itself, but what that item/animal/etc. represents.