Cake and pizza can be both countable and uncountable (so you can be always eating pizzas or always eating pizza). But always eating beefs/beeves doesn't work because for most people today, beef can only be uncountable.

Thanks, it's hard to come up with definite examples. This seems to be one of those areas of language where each word just has its own "feel" for what is proper.

I think you'll find that most decent dictionaries do tend to say if any given noun is (always, or only sometimes) uncountable, if only because it often affects the precise meaning.

Because few people eat more than one cake, or even a whole cake, at a sitting? So the amount of cake you eat is an undefined, more or less infinitely divisible quantity, whereas (working) cars are unitary, So you'd say e.g. "I love strawberries", because you normally eat a number of them, not just part of one.

@jamesqf First of all, you can eat three cakes. They could be small cakes like cupcakes, And they needn't be sweet. You say I love strawberries the same way you say I love movies.

@Lambie: Sure, but that's not the common case on which the language is based. I think in that case a person would be more likely to say something like "I sure love these (little) cupcakes." But of course English is flexible: there are many different ways to express an idea, often with different shades of meaning attached.

Question title Why do we say “I love cake” but “I love cars” is ungrammatical. The but conjunction is like and, but requires contrast. For instance "why do we say X, but not Y?"

@Kaz: It's not ungrammatical - the contrast is between "cake" (singular) and "cars" (plural).

To say "I love cakes" would carry the specific implication that what you love is the type of cake that you can eat all of at once (e.g. cupcakes), to the exclusion of also loving e.g. sheet cake. But saying "I love cake" does not seem to carry the opposite implication.

@jamesqf Or relatedly, you can also "love strawberry" as the uncountable concept of its flavor.

@Kaz: What makes you think there has to be a "not" in there? There are plenty of ways that "but" can be used without "not".

@psmears I never stated there has to be a "not"; my example just works out that way. Okay, here is one without: "why do we ride motorcycles but drive cars?" See, that works, because the verb is different, so there is a contrast there. What we have here is something quite similar to: "Why do you like oranges, but like apples?"

@Kaz: It's not like "Why do you like oranges, but like apples", because "oranges" and "apples" are grammatically identical (plural improper nouns). In the question they're different ("car" vs "cakes" - singular vs plural); the questioner is asking why it is not necessary to pluralise "cake", but it is necessary to pluralise "car" to "cars" - that is the contrast that licenses "but".

@psmears Oranges and apples work fine in "why do you like oranges, but hate apples". I do not understand what the questioner is asking from the question alone. It's too cerebral; a pluralization detail between two pieces of embedded/quoted speech.

@Kaz: I agree that it's not obvious - and that emphasising the difference (perhaps by adding "(singular)" and "(plural)" after the relevant words, or similar) would make it much easier to understand. But unclear isn't the same as ungrammatical :)

@psmears Understanding doesn't help; in spite of understanding it, it doesn't emerge as grammatical. This is in contrast to, for instance, "Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo" which becomes grammatical when you figure out, or otherwise obtain, the proper parse.