It's not about the size of the business, but whether this is a good way for them to spend money or not.
Coffee shops will often not get back to you within 48 hours depending on the comment you make and how busy they are. It's really a judgement call, as large number of comments are basically spam, but you can't reply with "this is a silly comment" or "this is an unreasonable request on our time", so it's best to just ignore.
For a big business, where individual judgement is replaced with a set of procedures and institutions that try to encode judgement, they most surely will offer some level of support with an SLA that guarantees someone will get back to you in a well-defined period of time.
But you usually have to pay extra for that, and that's a pretty sensible system, since leaving comments is free and there is no way to know how serious you are about the comment and how badly you want it responded to. E.g. worth paying, say, $10? $5? $1? There is some intersection of supply and demand for real support at which a certain price results in you getting answers, but in those situations where that price is not zero, it's not the size of the business that matters, but the shape of those supply and demand curves. And the size of the business, in my experience, will tend to shift the supply curve farther away from "free", because that answer will be an official answer of the business and it may take a lot of time for the poor support guy to track someone down and get an official answer, and in some cases it may be a lot of work to get that answer if the bureaucracy is complex and knowledge is stovepiped. This is why you see tiers in support, and the time required to get someone knowledgeable is often much longer as you climb that support chain and escalate your question. All of that ends up costing quite a bit to a big firm.