The .380 is not an ideal defense cartridge, but it ain't goin' away anytime soon because of the portability that some of the smaller pistols have. The SAAMI pressure limit for the .380 ACP is 21,500 PSI and cartridges that are loaded higher than that like Buffalo Bore are definitely +P.
What you have to take into consideration are the 2 different locking systems employed in .380. The Blowback types are the most encountered and I'd stay away from +P if I had a Blowback operated Pistol. While Ruger may not recommend the use of +P in the LCP, it is a Locked Breech design like the majority of larger 9mm pistols and it is the stronger system. While I might not rush out and buy Buffalo Bore +P ammo for it, if I had it I would fire some rounds to prove it functions and carry them if they were loaded with a JHP bullet like the SPEER Gold Dot or the 102 gr. Remington Golden Saber.
Locked Breech .380 pistols are becoming increasingly more available like the SIG/Sauer P-238, Colt Government/Mustangs and the new Ruger LC 380 among others and if I carried a .380 pistol it would be of the Locked Breech type in order to use higher pressure JHP loads, some of which do pretty well in various gel tests.