Teams also have 8 man bullpens nowadays, which makes reducing starter workload possible. Most teams also carry 20+ pitchers on their 40 man roster, giving them quick access to even more depth.
The reduced workloads are not exciting, especially for those of us who remember 4 man bullpens and 1,000 IP from the rotation. But unfortunately with the money tied up in SP, teams mitigate any risk as much as possible. And for a pitcher, nothing is riskier than pitching. (Ok, maybe base jumping.) Especially with how hard pitchers throw today vs how they threw just 20 years ago, let alone 30-40 years ago…