This has to do with countable vs uncountable nouns. Wine is a tricky example here, because it has two plurals meaning two different things. A lot of wine could refer to a large volume of wine, where a lot of wines refers to a large selection.
Let's try sand vs rocks to make it more clear cut.
There is a lot of sand
We say this because sand is an uncountable noun. It would be insanity to try to figure out exactly how many grains of sand there are in a given pile, which is why the term grain of sand exists in the first place. Sand is inherently plural, but you couldn't say there are a lot of sand because that implies there is a fixed number. However,
There are a lot of rocks
Here (not counting gravel), you can ascertain in a finite amount of time just how many rocks you're talking about. Because it is possible to determine the number, it is a count noun, and as such is pluralized with are.
Edit for relevance:
As with a lot of, some other words denoting a generalized plural have to be decided on a case by case basis. It typically has to do with whether grouping the object creates a new object per se, e.g. there is a bunch of grapes over there vs there are a bunch of cats in the other room.
Others, though, refer to either a fixed amount or are a noun in and of themselves, e.g. a pair of or a group of, respectively. These are treated as a single unit.