"Training" the shoulders just doesn't mean much. Bench press and overhead press is "training" the shoulders. Rows are "training" the shoulders. That won't, for example, protect you from impingement. Hell, just the opposite. If you are prone to impingements that will bring it on.
Hmm....my guess is more people than not don't use proper technique on bench. Also, for sure, more people than not don't use proper balance around the shoulder complex. Maybe it's us guys with bad shoulders who have to learn the real deal with them. Some of us just reach threshold earlier than others...so much has to do with all the baggage we carry from our lives and habits...everything, not just training.
Here is some of the misinformation that plagues us from yesteryear.
1. You train all the "delts" and that will keep your shoulders happy.
2. You balance your pushing and pulling and that will keep your shoulders happy.
3. You do some "rototor cuff work" and that will keep your shoulders happy.
4. Or my favorite. Laterals keep your shoulders happy.
For every guy who does what he wants for 20 years with nary a problem there is 5 more with shredded shoulders. And a lot of them tried to be careful.
As far as bench pressing...the best variey to use is not just changing angles but changing to dumbells. The straight bar is not your shoulders friend since it forces you into a less than optimal grip as far as your shoulders are concerned. If people would stop relating exercise variety to "what it does to your muscles" and start relating it to what it does to you health and your ability to continue to lift heavy weights it will make a huge difference in the way we think.
I am not saying this is the only reason for variety of course!
One last closing thought before I get off the stump I TRY to make it brief
For some this will be an "Duh, Eric, we know that" and for others it will be a new concept. When you are lifting weights regularly, espcecially compound complex movements, just because you CAN lift the weight, and even a very heavy one, DOESN'T mean that everything is working as "designed". The brain and nervous system has an amazing ability to adapt to inefficiencies and weaknesses in order to GET THE JOB DONE. One muscle in a "group", say for instance the internal rotators (with the subscap thrown in) is being shut-down for whatever reason then another muscle simply has to take up the load. This goes on for long enough and BAD THINGS HAPPEN. When you relate this to the shoulders, the most compicated an misunderstood "joint" in the body it is even worse.