Why should we have moved to 3D? 2D was never an issue. Why should we improve graphics? No one complained about it in the SNES era. Why should we have stories in our games? Atari games didn't have any.
It's because the medium progresses. There isn't really a reason for Pokemon to not have voice acting, other than them not giving a shit and saving the money. It was obvious why they didn't have till the DS/3DS due to technical limiations, but on the Switch, it is more than capable of handling voice acting and the pisspoor stories could be improved by the characters expressing some sort of emotions via voices, since they always do the same 3 animations anyways.
Not to mention, Sword/Shield literally had a scene where one character was supposed to SING and they thought "yeah, we don't have any voice acting, but let's implement a gym leader "singing" ". The DS atleast had pseudo singing in on of its Pokemon games (don't remember which) via midi sounds