Because the stories are primarily made with a Japanese audience in mind? Also, the rest of the world (Including West Asia, Africa, and South America), and the French, are actually very extreme weebs that would make even the biggest Japan-ophile in the English speaking world very uncomfortable.

By the way, actually decided look through my wishlist of series that have come out in the past 5-6 years (Over 600 series), and these are the only ones that have ridiculously long titles:
-Mom, Please Don't Come Adventuring with Me! ~The Boy Who Was Raised by the Ultimate Overprotective Dragon, Becomes an Adventurer with His Mother~
-The Banished Villainess! Living the Leisurely Life of a Nun Making Revolutionary Church Food
-A Story About Treating a Female Knight Who Has Never Been Treated as a Woman as a Woman
-I'm a Middle-Aged Man Who Got My Adventurer License Revoked, but I'm Enjoying a Carefree Lifestyle Because I Have an Adorable Daughter Now
-Self-proclaimed ordinary demon's heroic life: The result of him creating a cheat dungeon, even though he's supposedly a B-grade demon
-Yowai 5000-nen no Soushoku Dragon, Iware Naki Jaryuu Nintei Yada kono Ikenie, Hito no Hanashi o Kiite Kurenai
-Reincarnated as the strongest wand In another world, I'm forcing a girl to be a magical girl against her will!
-I've Became Able to Do Anything with My Growth Cheat, but I Can't Seem to Get out of Being Jobless (Novel)
-Toaru Majutsu no Heavy Zashiki Warashi ga Kantan na Satsujinhi no Konkatsu Jijou (Novel)
-For My Daughter, I Might Even Be Able to Defeat the Demon King (Novel)
-World End: What Do You Do at the End of the World? Are You Busy? Will You Save Us? (Novel)
Even looking at ALL the documented series listed on this site that have started in 2019 alone (Almost 700 series), only 11 have extremely long titles.

Also, an interesting thing that I noticed is that while all those titles are long, they use up to three times as many characters in English as they do in Japanese. For example, "Mom, Please Don't Come Adventuring with Me! ~The Boy Who Was Raised by the Ultimate Overprotective Dragon, Becomes an Adventurer with His Mother~" is 145 characters in English, meanwhile it's original title, "冒険に、ついてこないでお母さん！ 〜 超過保護な最強ドラゴンに育てられた息子、母親同伴で冒険者になる", is just 50.

Also, what about how we have long titles in our own media as well (With shorthand titles) such as "Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb", "The Chronicles of Narnia: The Lion, the Witch and the Wardrobe", "We Can Remember It for You Wholesale" (Which became Total Recall), "Max Payne 2: The Fall of Max Payne - A Film Noir Love Story", and "The Second Part of Henry the Fourth, Containing his Death: and the Coronation of King Henry the Fift" (That is not a typo).