Couple of issues to start.
There are small barrels called barriques and there are large barrels that go by different names; In Italy, they're called Botti. In France, they can be called Tonneau or Foudres. Sometimes the large barrels are simply called "casks."
Size matters and so does the % of new versus old barrels.
Why?
Because a small new French Oak barrique will impart more oak flavor to wine than a large barrel that has been used at least once already -- because that barrel will have already imparted much of its flavor and will have less left to impart to the next vintage.
Next, there are different types of oak; French (with a few different sub-types), American and Slavonian.
The French started using high % of new French Oak barriques for Bordeaux and Burgundy.
The most influential Wine Critic in the world is a fellow by the name of Robert Parker.
A high score from Robert Parker will literally move the market causing the demand and price of a wine to skyrocket.
Parker made his reputation originally from scoring Bordeaux wines using his 100 point system, since copied by others.
From the mid-eighties onward, Parker wrote tirelessly, telling the wine world how much he appreciated the flavor of French Oak, how he felt it improved the complexity of Bordeaux and strongly urged Napa Valley Cabernet producers to use it.
Parker also enjoys highly concentrated wines and high alcohol wines.
This is my opinion, but you will find many in the wine world who agree and some who disagree.
Some who agree are anti-Parker, some who disagree are Parker apologists and then there are people like me;
I have nothing against Parker. I have purchased plenty of wine on his recommendation and have enjoyed a lot of it immensely.
In the beginning, Parker's influence was probably a good thing -- he encouraged producers to improve the quality of their wines and he rewarded them with higher scores when they did.
However, as you may have noticed, now, more and more wine from around the world is being aged in small new French Oak barriques.
It is said that these wines are being designed for "International" tastes.
It is also sometimes said that these wines are "Parkerized."
Funny thing is that Parker is not the only wine critic who rewards wines with high % of new French Oak and many wine drinkers do enjoy the taste of French Oak.
So, other critics (Wine Spectator) and consumer demand must also share some of the blame.
To me, there is no doubt that new French Oak can impart delicious, complex flavors to wine, but if you are into wine and like to drink different kinds of unique traditional wines from around the world, it can be a little monotonous to find that the Sangiovese you used to drink from Montalcino that was traditionally aged in giant Salvonian Oak Botti is now being aged in small new French Oak barrels and you lose a link to the traditional regional character of the wine and damn, there's that French Oak flavor again. You get tired of it.
One other issue;
Bordeaux and Burgundy wines traditionally were meant for long aging. We're talking decades. If you can cellar them, you'll end up with an incredible wine -- and -- for the purposes of this discussion, the point is that decades after the bottled wine has been aging in your cellar, the French Oak flavors will have become very, very subtle, blending into a tapestry of flavors that are woven together so fine that it is much harder to distinguish the original French Oak flavors.
But, Parker's push for riper (some say over ripe), more concentrated grapes has also meant that these wines often can now be drunk much sooner.
Add to that, a small % of wines are meant for long aging. It takes a lot of fortuitous events to create a vintage that will age for decades.
A lot of wine is not built to age that long.
That wine will never have a chance to absorb all of that French Oak.