D&D has a long history of first level characters being very easily killed by goblins, kobolds, rusty nails, or semi-domesticated house cats. Some classes remain squishy and death prone well into 2nd or even 3rd level.

While D&D is not unique among RPGs in this respect, what is interesting is the change from squishy to non-squishy as characters become harder to kill if not impossible to actually drop. Other games tend to be more consistent,  with characters always being hard to put down or always fragile and death prone.