Wikidata is different from verifiability for Wikipedia. One sentence like "Mr X was born on 7-5-1959 in Zwaag, he became known for activities in Y" contain multiple statements and Wikipedia could use one source while Wikidata needs the same source multiple times. The sources for Wikipedia are nice out of the way and for Wikidata they are in your face.
Yet again there is a discussion about verifiability and to be honest, it is boring. On a typical day the vast majority of new statements come without any sources. To be brutally honest, I have never added sources and I do not intent to either. I do remove sources when I update information that is wrong and is sourced.
Wikidata is hardly the only source of linked data and it is relatively easy to compare databases. This is when the idiosyncrasies come out. It is where you have to map data from one database to another. Once this is done, you can compare multiple sources and find how they match and mismatch.
Arguably this is more powerful as individual sources because there is little interest in adding missing sources per statement. There is a lot more interest in finding out why there are differences between the data in databases. It leads to a finetuning of the mapping or it leads to changes in the data on either end.
Wikipedia does not need sources for each Wikidata statement. What it needs is confidence. Confidence in best practices that ensure the data is as good as we can make it.