Why doesn't J4 or Vi percent health physical damage on-hit proc lifesteal?

and (let me know if there are more) seem to have special cases where their percent health passives specifically do not proc lifesteal. used to specifically not proc lifesteal on its own on-hit damage but they got rid of that limitation. gets to proc lifesteal on its on-hit damage passive.

It seems more recent changes show that Riot is moving away from being scared of sustain from percent health damage. Even right now both and can build and even and still heal from their percent health damage, and it doesn't seem to be overpowered or anything.

I think these artificial limitations are a relic of the past and should be removed.