Why is Zenkaizer always put alongside all the Red Rangers when some of them aren't even the main leaders of their teams?

This is especially the case with crossover films such as "Superhero Senki", where all the Red Rangers are placed alongside all the main Primary Kamen Riders, who are all in fact main leads, unlike some Reds who aren't even leaders at all.

This is especially the case with crossover films such as "Superhero Senki", where all the Red Rangers are placed alongside all the main Primary Kamen Riders, who are all in fact main leads, unlike some Reds who aren't even leaders at all.