Just because you can carry something in Condition One doesn't make it a good idea.
The Walther PD380 is an extreme example, sure, but most DA/SA guns that can be carried "cocked & locked" really aren't optimized for it. Safeties are often less than ideally ergonomic for the task (heck, the original GI M1911A1 thumb safety ain't that hot; the giant aftermarket for improved ones wasn't just for cosmetics.)
Further, they are often lacking in a serious detent to keep them in the on-safe position. Few things are as puckering as discovering a cocked and unlocked pistol in your holster. It's not like a modern striker-fired pistol intended to be carried that way. Many pistols of this type, especially older ones, have hardly anything in the way of passive safeties when cocked.
Learn to shoot double action for the first shot. De-cock between strings at the range. It's not a difficult skill.
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