Because then the US was at the “end of history”, they thought they had won.
Beside, there are two more reasons. 1. Any actual attack on DPRK had significant chance of involving PRC, and 90’s USA would rather not do it since they thought China is liberalising and will end in their pocket sooner or later (also it would disrupt all the US capital invested there) and 2. DPRK, while being completely harmless to USA, is actually very useful to their propaganda, which was especially true in the 90’s after destruction of USSR - it provide them with what every fascist regime needs - an external enemy - and it’s a great external enemy, the embodiment of “other”, mysterious, dangerous, dehumanised.
Because then the US was at the “end of history”, they thought they had won.
Beside, there are two more reasons. 1. Any actual attack on DPRK had significant chance of involving PRC, and 90’s USA would rather not do it since they thought China is liberalising and will end in their pocket sooner or later (also it would disrupt all the US capital invested there) and 2. DPRK, while being completely harmless to USA, is actually very useful to their propaganda, which was especially true in the 90’s after destruction of USSR - it provide them with what every fascist regime needs - an external enemy - and it’s a great external enemy, the embodiment of “other”, mysterious, dangerous, dehumanised.