I'll bite. Because of the way ESO plays out there are only a handful of abilities with cast times, majority of abilities are instant cast, no cooldowns, no alternative playstyles like combo point generator/spenders, no true synergy like I stack X debuffs on target and Shatter their Armor with Y ability; it's all very simplistic and straightforward.

What you'll end up doing is stacking more of the same abilities regardless how many button slots you have per bar and rarely will you use more than 1-2 direct damage spammable attacks per bar where other MMOs have 3-5 such abilities available that you have to rotate around, having more slots in ESO however doesn't change anything. There's no penalty, drawbacks, or on the fly decision to use one ability over another, you're not waiting for a proc to boost a skill from using another, or chaining a pattern, no real build up between what order to use them.

Would I like 2 slots reserved for passive abilities that give you a buff while slotted, sure! It's not going to happen, real estate management is one of the ways they balance their game since they have no restrictions on when you can use something. Everything is generally always available, you getting more slots just means you'll use more of the same abilities without any changing dynamics.