Perhaps that's because middle infielders are just much larger than they used to be years ago. Who knows.
I don't think there is any doubt that is part of the reason. Shortstop was once considered a skill and finesse position. A solid fielding shortstop was worth his weight in gold back in the day. These days you have teams like the Mets who were willing to put a mannequin like Wilmer "Cement Shoes" Flores out as their regular starting shortstop one year because they thought he would hit enough to offset his immobility. Turns out that he didn't, but you live and learn. You once had guys plugging the middle with nicknames like "Pee Wee" because they were small, lithe and (for the time) fast enough to cover all the ground. That matters a whole lot less these days.
The Braves had a young shortstop prospect a few years ago, Andrelton Simmons, who was an incredible fielder. The kind of guy you can see winning Gold Gloves at the position for 10 years. But, he didn't hit enough for them (although in his first full season he did manage to knock in 17 home runs, but hasn't even hit 10 since). They traded him to Anaheim.
Second base is even worse. That used to also be a finesse position, but now you see a lot of bruisers manning second. The Marlins and Braves both trotted out Dan Uggla for a few years to play 2nd. That guy is a hulk. At one point he was putting up 30 home runs a year. Can you name a 2nd baseman when you were growing up who could hit 30 homeruns a year? Or 20?
It's a different game and one of the thing that has come form all the analytics is a lot more emphasis on power and a lot less on defense. I think that is starting to come around a bit, after the Royals went to back-to-back World Series with a team built on speed, defense, and very little power, but most teams are built to have power everywhere. It just didn't used to be that way.