Because by his logic, ToL has always been a situational form that was NOT part of the core druid forms (of which it was only Cat and Bear, which only had uses for levelling in Vanilla, and saw much more play in TBC). It is a form similar to Shadow Form for a Priest - You sacrifice a part of your spellbook in order to focus on doing something better. This was what its purpose was in TBC. In TBC, you never saw a Resto druid ALWAYS in his ToL form BECAUSE it had distinct disadvantages. Not even in PvE do you always see a Resto Druid in ToL form, because mobility was important as was the form of CC that a Cyclone might provide. And in arenas, no self-respecting resto druid would use it for PvP for the same reasons

In WOTLK, we're so used to Resto druids being in ToL form that we think of it like how Feral Druids use THEIR forms.

Case in point, the Feral tree consists of talents COMPLETELY DEVOTED TO IMPROVING THE FERAL FORMS OF BEAR AND CAT. They provide NO benefit to a Druid's ability in caster form. For a Feral Druid to BE a Feral Druid, he MUST be in a Feral form or else the entirety of his Feral Talent Tree AND the Feral portion of his Spellbook are completely useless.

Resto Druids' talent trees affect his healing capabilities in the same way as other healing classes. They affect spells and effects that he can take advantage of in his CASTER form just as well. As GC stated, ToL was added in TBC, it was NOT a defining point of the Resto talent tree at all. ToL was a way for a resto druid to buff himself but at a disadvantage. A disadvantage which has more than been removed in WOTLK, making Resto druids think their default form SHOULD be the ToL form.

Yes, there are resto druids that enjoy it, I don't think anyone is saying the decision is fair to those people. But a lot of people are over-exaggerating the actual importance of the ToL form.