There is a global squeeze on Alcantara. Their supplier (who probably already disliked them, based on the common knowledge of how Tesla treat suppliers) decided to tell them to take a hike with their relatively small orders (with a delayed volume ramp up as a further annoyance) and instead decided to focus on their larger clients like BMW, VW, etc...... AKA they decided Tesla wasn't worth the headache.
How does Tesla treat suppliers? And how is that different from other manufacturers?
Not that many people.
The problem is, it is a sign of things to come: ordered and paid for cars that get delivered with different options than ordered, for things that matter. It happened before with seats on the Model S. A lot of that was fixed, but it seemed like it took forever to fix for a lot of people, and a lot of people seemed like they couldn't get it fixed. It could happen again with the Model 3. All of the currently configuring Model 3 customers are previous or current Tesla owners, so they're mostly familiar with this issue, and know what it means. Very few of them care hugely about the cloth vs. suede, but it is just one of those things that is a sign of trouble to come. However, I hope that this is just a little hiccup along the way, rather than a sign of future problems. I think Tesla tried to learn its lesson with this and not make this mistake on the Model X, and from what I can tell, it did pretty well on that.
Assuming they could not get the Alcantara, as others have posted, then what was Tesla's alternative? Delay the car yet again, making a lot more people a lot more upset?
A lot has been said about Alcantara being the stuff used in luxury cars. I've never regarded the Model 3 as a luxury car. The Model 3 is a long-range, zippy electric car for people who don't want or need the luxury and/or size of the Model S. Tesla makes a luxury car: The S. Now they're starting to make a car that, when the base model becomes available, will deliver peppy performance and over 200 miles of range for $35,000, which puts it into the price range of a lot of ordinary people who want to join the electric revolution but could not afford Tesla's offerings up until now, and don't want to accept the compromises of the other manufacturers.
The Model 3 is not a luxury car and is not intended to be a luxury car, and people are making a mountain out of a mole hill with Alcantara in the headliner of a car that has a glass roof and hardly any headliner to begin with. They made a call to go ahead and build cars with the material available rather than delay them even further. And they're providing more and better service than any other U.S.-based car company and most world-wide.
If you really need to have Alcantara, there are cars you can buy that have it. And if that's your deal-breaker on the 3 then please cancel your reservation. And if you already have your 3, and you were expecting Alcantara and you got cloth, I'm sure Tesla will take care of you. Or you can still sell it for a big profit and buy something else or wait for Alcantara to be available. Sheesh, people, this is really a tempest in a teapot.