There are several reason's why cork fail as enclosures for wine bottles. The most common is due to TCA which taints the wines with odor and aroma resembling wet cardboard. TCA is a compound created during the processing of cork it self (bleaching) or it can be created on the cork tree itself as a result of e.g. a chemical reaction with herbicides or pesticides.
We have experienced a fair amount of problems with TCA, in severe cases with as many as 1-2 bottles per case which is about 10 times more than typical occurrence. TCA is not visible on the cork itself, but can easily be smelled on the cork or in the wine glass. Most wineries are constantly looking for enclosures that behave like traditional cork but without the TCA contamination risk.
The other problem is leaking corks as seen in the photos above. Leaking by itself is not necessarily a problem, but it opens up for problems as leaks create a transmission channel for unintended transmission of e.g. oxygen or worse transmission of bacteria etc.
Finding the perfect cork / enclosure is a tradeoff of oxygen ingress, potential odor contamination (besides TCA in natural corks it can be a problem with synthetic corks due to the material) and the potential for leaks. In many cases the result will not be visible until the wine is aged well. That makes the choice of corks / enclosures a really important task.