Depends on the topic. Sometimes when it is a complicated topic or one of factual question and we are not experts we quote someone who is.
For example- I am not a physicist. In a discussion about cosmology I might quote Lawrence Krauss or Neil deGrasse Tyson because they are experts in the field of modern physics.
One must just be careful not to commit the Argument from Authority fallacy. Krauss, for example, is an expert in physics. That does not mean his expertise transfers to other topics like history or art, just because he is intelligent and well respected in his field. We often see this fallacy here when a Christian quotes a famous person who believes in God to lend weight to the idea god exists. Just because, say, Isaac newton believed in a god doesn't make it more likely to be true.
Any quote should be accompanied by a source which includes the context from which the quote was taken so it can be checked. Opinions are good to express, but you are right that the views of an expert in a certain field can add weight to that opinion--particularly if the quote comes from someone who would logically be supportive of the contrasting opinion.
It depends on the creditability of who and what is being quoted; Is the truth being quoted or just some one else's opinion? If it is the truth who's truth is it? What is the source? Is it God or is it man? Something to think about.