I think that a certain amount of siloing can be a good thing. Having combat and non-combat abilities somewhat segregated reduces min/maxing, making it easier for new players to contribute just as much as old hands. Also, it decouples two things that are generally not related (combat and non-combat abilities).
There are a lot of character concepts that are difficult if not impossible to implement properly without siloing. For example, the master swordsman who is also a writer, historian, and calligrapher. If you want to build that character in a system that does not differentiate between the two, you would have the disconnect that the character must be less of a swordsman in order to be a writer, historian, and calligrapher. In a system that separates the two completely, however, the character can be the greatest swordsman possible, and also the greatest writer, historian, and calligrapher possible. I note that 4e is not a fully siloed system, since stats affect both combat and non-combat abilities, and so which stats a class needs for combat will push them towards being better at certain skills. Also, as has been pointed out, the feats and utilities overlap between combat and non-combat abilities.
As a side note, I find it interesting that the OP posted Magic Missile, Mage Armor, and Shield as top first picks for a Sorceror and Grease as an odd choice, as I've always considered MM, Mage Armor, and Shield to be poor first choices for sorceror spells (MM does too little damage, MA and Shield don't last long enough to matter, MA is only worth picking up when it lasts much of the day), and Grease to be a top first pick (it can keep several enemies out of the fight for awhile, and doubles as a way to help allies escape grappling monsters).