See fallacy of equivocation
for why it matters in debate.
"Socialism" as the primary economic system has been widely criticized and is rejected by the majority of Western society.
However in debates about social programs it is often tossed around for its rhetorical effect, ignoring that doing so is to move the goalposts and render "socialism" meaningless by equating it to any social program.
These things have real meaning, and quite often in political debate ambiguity of definitions are exploited to make intellectually dishonest points. They are employing the negative sentiment against a socialist state in order to make cheap political points against a particular social program.