It's more that it's just more work for the DM in this case. Every time a skill check is called or considered, the DM has to reconsider if the character considers this a routine or trivial task. You can see this in the stats: if the character's modifier is 5 or less than the DC, it's trivial. But you also must consider even without a high mod vs DC, is this a task the character has performed hundreds of times before? I try not to come up with solutions, or utilize WOTC solutions that make a lot more work for the DM. Especially if there's already a rule or slight tweak that makes sense and prevents this work: in this case, no crits for skill checks.