Sword styles in popular culture come and go.
The katana's popularity probably is related in part to people taking them home after WWII and then years later finding out how valuable they were, making collecting katana popular, even though most modern reproductions are not valuable.
Another factor is the popularity of Japanese martial arts. Many practitioners like to have working swords for training, cutting practice, or just to have. I've also known many martial artists in arts that don't use the katana who like this style of sword.
In contrast, while fencing is popular in colleges and community centers, the average fencer has no desire to buy a real rapier or sabre. If fencers did buy sabres and rapiers at the same level practitioners of Japanese arts bought katana, then they'd probably outsell katana.
Some people just like movies and buy the swords from the movies, or ones that look like the ones on the movies. I the main characters on the "Highlander" TV series and movies used sabres instead of katana, sabres would probably be more popular than they currently are. The gladius was popular when "Gladiator" came out, and two-handed swords when the "Lord of the Rings" series was being shown.
I always considered a good quality sabre to be an effective melee tool. Especially the more modern designs. Given that armor is fairly non-existent these days, I would think a single handed implement with a suitable guard would be preferable in most cases..
A bolo, barong, machete, kukri, etc. would be more practical since they can also work well as tools, some of them being agricultural tools.
When was the last time a sword of any type was used at least marginally in battle (major conflict)? I'm thinking it's been at least 100 years now.
Guerillas in the Philippines still use Filipino blades, and they were used against the Japanese in WWII, and against Americans before that.
Machetes are popular weapons in Africa.