Why is it "spend" and not "spending"?

The same reason it's "ask" and not "request"

aviraldg an hour ago | parent | prev | next [-]

I've mainly seen it used this way in business contexts

abirch an hour ago | parent | prev [-]

spend is a noun in this sentence. As a noun, spend refers to the amount of money spent for a particular purpose or over a specified length of time

	▲	prewett 26 minutes ago \| parent [-]
		Spending is also a noun. A gerund used to be the way you nounify a verb. “Ad spending” is perfectly grammatical, unlike “ad spend”. This seems to be part of a broader trend, not just business. One group of pastor-students would talk about giving a “preach”. Drove me nuts.