Modern equipment has made the game faster and more physical compared to the tennis of old. Add to that the fact that there are so many tournaments these days on hardcourts instead of more forgiving surfaces like grass and clay plus the reasons already mentionned by the OP and it's easy to understand that so many players get injured.
This is THE
one thing I have found extremely difficult to understand.
I thought there was a study in the early Noughties (2000s) that stated that Hard court Tennis was punishing on the body and ushered in more injuries - am I imagining that?
I also remember in 2005, Jim Courier was interviewed on BBC during Wimbledon championships and he expressed the view that one of the reasons why less players are playing an all court game or can volley well was due to the fact that most of the Indoor carpet events were becomming extinct and hard courts were now as slow as clay in many instances.
And yet, more than ever, they are now playing Hard court events all year round!! First, since 2008, the Australian season is now on Hard court as opposed to rebound ace (a more rubberised surface laid over concrete). Then there is the American Hard court season in Indian Wells, Miami and a few other smaller events. Then there is the summer Hard court season from July to September. After that there is the Asian Hard court season from September to October.
Then after all of that Hard court Tennis, the season now finishes with - Guess what? Hard court year end tournaments in Doha and Bali!
The other thing to consider at least on the WTA tour, most indoor tournamenst have also actually switched from carpet to Hard court, so there is really no escape.
We know Hard court is low maintenance but you really have to wonder whether the Governing organisation has the best interests of its players at heart by asking its players to play on Hard courts so often all year round, year after year.