Its important, but its doesn't have to be constant.
IE: If I get a message that there's a problem and that I'll get an update down the road when a feel for the time frame to resolve it is available, I'm typically good to go on a provider I've got a relationship with.
If I know nothing about a provider, I might either simply not use them...or, wait and see if others have, and what their experiences were, etc...and then make a judgement call.
If from personal experience, a problem I could see taking a month to resolve is mentioned, I will mentally adjust to a month or so....if the delay is setting up a new work area/shop...a week or three could be reasonable, if the delay is a 1 week vacation, then a week should be about right, and so forth.
If its a seller I don't trust, again, I don't do ANY business with them...which avoids me risking things I don't want to risk. I try not to fly higher than I can afford to fall. For example, lets say I buy a $600 light...and I GET IT, and its AMAZING, but, I drop it off a cliff and it makes a distant "Wiley Coyote" puff at the bottom of the grand canyon, etc...and its ruined....I'm STILL out EXACTLY the same amount of money as if I never received it. I would be really really PISSED either way of course...at myself if I dropped it into the grand canyon, and at the seller if I never received it.
The difference is I might have SOME recourse if I never received it, and might one day get my $ back. With my luck, I'd be fined for littering in the grand canyon though.
As a business owner, I personally make sure I get back to people ESPECIALLY if there's going to be a delay or any change in what they might be expecting. But its my only responsibility...and I make it my priority.
I KNOW a ton of people who do things as side jobs...so they are working 40-80 hours a WEEK at "their day job", then coming home and trying to catch-up on their cottage industry/side jobs, etc.
Sometimes, they just can't keep up...you can't really call people back at 3 am...normally, and, you might have too many emails to get to them all, etc. Add to that that you need to DO that second job...and people get spread too thin when things surge. I have clients who mention that the send time on an email I sent them said it was 3 am or 4 am, etc...as I CAN email at that hour. I'll be mostly worthless the next day of course.
If you are getting things from people who do what you need from them as their SECOND JOB, you need to have different expectations. These are businesses that are done on a catch as catch can basis, and, knowing that, you can't expect large corporation-type response, because they typically just don't have the resources to do it. Typically, they CAN do it when things are what ever passes for normal...and if things get busy for a bit, its a surge they can ride out, etc.
But if business EXPLODES, well, they get blown up...and, need time to both react, and adjust.
Many CAN manage this, many have trouble with it.
Guys who are technically proficient are not always the best management types too, and while the product might be great, the running of the business end of things can suffer, ESPECIALLY if the production side gets overwhelmed, and they put their heads down and dig into the MAKING of the product, assuming HAVING the product is the real answer to the problem.
Manager-types see that the product delivered includes the plate its served on so to speak, and try to address the concerns of customers, even though they know it means they have to wait MORE....due to the lost time.
Its a double edged sword, and, well, some businesses, and some customers, do bleed from time to time.