For me, that falls under one of the handful of reasons under (1).
But yes, enterprise rollouts are just a different beast for any number of reasons (contracting, legal, compliance, industry certifications, security audits, etc.)
Perhaps under (1) as well but especially at large enterprises you will likely deal with internal politics in the potential customer organizations. If the right person likes your offering, that can grease a lot of skids. If they don't, or your internal champion isn't well liked, you will face difficulty. This is all entirely separate from whether your product objectively meets a need the customer has.
We talked to one potential customer and he told us that they had an internal team working on something similar and admitted that they were much further behind and the experience was nowhere near as good as ours.
I think that's why you need really warm intros at very high levels or you need industry gravitas to pull this off without a very, very hard grind.
But yes, enterprise rollouts are just a different beast for any number of reasons (contracting, legal, compliance, industry certifications, security audits, etc.)