They are coddled for a multitude of reasons, and the most obvious of those is that it works.
Every MLB team carries a minimum of 13 pitchers (vs. 12 position players) because that ratio works. Statistics emphatically show that hitters do better the 2d, 3d, and 4th time they face a given pitcher in a game. Pitchers are expected to throw as hard as possible within the context of having a good repertoire, which unsurprisingly can lead to arm/shoulder/elbow problems. Every manager needs options when the guy on the mound, whether starter or reliever, goes south on him. So he needs 5 starters and 8 relievers and nothing less.
Position players simply soldier on when they can't hit spit that day or night or make a couple of errors or whatever. Cal Ripken, whose feat is unlikely to be repeated, played not only a record number of consecutive games, but also a record number of consecutive innings. These days, the good position players are expected to do what Ripken did 95% of the time. To put it bluntly, MLB teams simply don't need more than 12 positions players.
Alex Cora is one of the few managers who actually prefers 90% and will take even his best players out of the lineup every so often. Here, for example, are the total games played (regular season only) on the incredible 2018 team: JD Martinez, 150; Benintendi, 148; JBJ, 144; Betts, 136; Bogie, 136; Devers 121.
Let's not forget, however, that position players do not exert themselves anywhere near the degree to which pitchers do. Every single baseball game is dominated by the contest between hitter and pitcher. If we assume 270 pitches are thrown in an average 9 inning game, the odds are that maybe 65 result in hits or fielded outs. The other 200 or so are just strikes and balls (which can lead to K's, BB's, HBP's, WP's, etc). Interestingly, every MLB team carries two catchers (except on the rare occasion when they carry three) because catchers do in fact exert themselves on every single pitch thrown. Incredibly--to me anyway--two catchers seems to be the right number despite the immense effort needed to play that position and the real risk of injury.