Should we (still) consider a synced XMLHTTPRequest bad practice?

Question

As you may know, XMLHTTPRequest can be used synchronously or asynchronously, but synchronized requests have always been considered bad practice, and I've always agreed with that.

Not only is the ideology of modern JS development heavily based on an event model, but there were also some more prosaic reasons to avoid synchronized requests. For example, old Internet Explorer versions could just freeze suddenly.

Today I saw a synchronized request in Liferay source code and thought "What a shame, how dare they. Don't they know that it is wrong?". But then I asked myself what is actually wrong with this approach in modern times, and I wasn't able to give an accurate, logical answer.

For example, on the server side it is common practice to use synchronized HTTP requests. Of course all the data could be fetched asynchronously, and perhaps should be fetched that way, but we often need data that will be used to fetch another chunk of data, so in that case the request must be synchronized.

So, should this still be considered bad practice?

PS: I haven't used the term AJAX since the first A stands for asynchronous. :)