>>38678147While that's true, you also can't leave Spear Pillar without facing them (Dawn and Rowan block you and you can't use Fly or an Escape Rope), unlike any other Legendary in the series. That means you can't heal your team, restock on Balls or anything before you face them—raising their catch rate was mostly a convenience for people who didn't know to be prepared because there was no way out.
Platinum, HGSS and ORAS fixed this by not being utterly stupid and just letting you leave in the first place, which strikes me as much easier; Giratina, Ho-Oh and Lugia had the standard Legendary catch rate of 3 as a consequence, and I want to say Kyogre and Groudon are 5 for some reason?
And then BW, XY, ORAS (for Rayquaza, not Kyogre and Groudon) and SM all keep you from progressing without catching the Legendary, so they have elevated catch rates (30 for Zekrom/Reshiram, 45 for Xerneas/Yveltal/Rayquaz/Solgaleo/Lunala). Note as an additional commonality that, in all cases except SM, there is another boss battle directly after the player catches the mascot with no time to save in between (N and Ghetsis, Lysandre, Zinnia and Deoxys), which probably also influenced the raised catch rate: although, in all of those cases, the player is either able to try again by coming back or is able to keep playing after they lose, it's VERY common for players to soft reset without thinking as a reflex when they lose a battle, and the upped catch rates act as an anti-frustration cushion for those who do this and then have to catch the Pokémon again.
Also, in BW and SM specifically, the Legendary has literally accepted you as its Trainer in-story before the fight anyway, so I don't know why you would expect them to be hard to catch. (And USUM Necrozma has the highest possible catch rate—255, meaning a one in three chance to catch with a normal Poké Ball at full health—because it literally owes you its life and wants to leech off of your Z-Ring. It wants you more than you want it.)
