"Why not order more pizzas?"
Translation:Kial ne mendi pli da picoj?
In English we use the bare infinitive in this situation too, though I never realized that until now... Can somebody explain why? I'm not sure I'd recognize the need for it translating from Eo to En.
I'm afraid it will be a disappointing answer to you about EN, but the answer in EN is just after the question word why, you use the bare infinitive.
Here is a quote from a post at (http://forum.wordreference.com/threads/bare-infinitive-or-to-infinitive-after-why.2533407/)
Linguistically speaking, you and your interlocutor are still at that stage in the exchange when notions, concepts, ideas, etc. are still being negotiated. It is a stage at which grammaticalization is kept to a minimum because what counts is, as I said, the "notions", which are the territory of nouns and verbs. The interesting thing is that, once the stage of negotiation has been passed and the "notion" (in our case "study German") stipulated by both parties, then whatever further question should follow, it will contain the operator "to"
Because "da" is a preposition.
Specifically, it's what I like to call a "relational" or "non-locative" preposition. (That is, it doesn't describe a location like in, on, under, between...) These relational prepositions (al, kun, per, da, de, por, je, pri and others) never require or allow an -n on the noun expression that comes after.