Characterizing striker-fired guns as "safety-less" is generally not fair. Most striker-fired guns have a number of automatic safeties (drop, striker blocker, etc.) that protect against accidents and misadventure.
What current striker-fired guns generally lack is a type of safety mechanism to prevent, or at least discourage, a user from pulling the trigger. It is worth noting that striker-fired guns were originally generally single-action designs (i.e. FN 1910, Savage pistols, Lugers, etc.) that did have manual safeties.
When double-action designs were applied to hammer-fired semi-automatics, manual safeties could be dropped because a long, heavy trigger pull acted as a safety mechanism, just as it did with double-action revolvers.
Credit Gaston Glock's marketing genius with the elimination of manual safeties from most striker-fired guns. Glock's design allowed his pistol to be called a double-action to satisfy police administrators (and lawyers) while providing a relatively light, although still somewhat long trigger pull that users liked.
At one time, it was axiomatic that a 5-pound or lighter trigger, which happened to be the weight of single-action triggers, needed a manual safety. It was also generally accepted that a 10-pound or heavier trigger, which happened to be the weight of double-action triggers, provided enough margin of safety to dispense with a manual safety. Once you convince yourself that a lighter "double-action" trigger is safe, it is easy to rationalize further reducing the trigger pull weight.