I don't know exactly when the features arrived, but things like xlookup, power query, live data connections, etc have been welcome improvements in Excel.
Bit of awkward phrasing, but the commentator was not talking about Steam exclusivity - rather having it available on Steam (in addition to wherever else it was available).
Clearer wording may be "if only it had been on Steam".
Can't miss what you don't know. I refuse to purchase at a laptop without a touch screen.
When you don't have a mouse it is great for quick interactions that cover a distance across the screen - interact with a button here, another over there, select a field far off from where my cursor is, screen skip, quick markup, etc. It's also far friendlier to use when commuting or flying where there are bumps and little elbow room. It isn't a 100% replacement for a touch pad but having it there to augment at times is such a boon.
They remember the one password that they use for everything.