Well, firstly, I don’t see 2 base-all-ins exclusively in TvP, unlike what we saw in PvZ recently. If it was really 70/30, that would be far more than enough for terran to do the whole same build 4 times in a best of 7.
But in any case, let’s look at the problem from the protoss side of things: protoss in current PvT is balanced around staying ahead.
In small scales, the terran army is more cost efficient than the protoss one, and when protoss doesn’t either have a tech advantage or significant army value advantage, the terran army is SIGNIFICANTLY more cost efficient. On the flip side, the protoss army trades cost efficiently when it is ahead in either tech or value, and the overall scale is reasonably large.
So how does protoss stay ahead in order to not just melt to the terran army? Well, partly chrono, but primarily warp gate.
Warp gate means that when terran attacks a protoss, the protoss is 2 whole production cycles ahead. Meanwhile, terran buildings lose their first production cycle to building add-ons, while protoss warp gates start off cooldown so they get a free production cycle upon completion. So when you see protoss just starting gateways, you have less than 60 seconds until those gates have each already produced a zealot. When you see terran start their barracks, it will be almost 60 seconds before they can start the reactor finally, let alone actually making units.
So protoss takes advantage of this sluggish terran infrastructure by taking a fast third. But what many terrans seem to miss is that they don’t just take a third because they can, but because they must.
Just look at how stim bio mauls equal cost of zealot/stalker. But of course, usually what we see is blink stalkers accumulating stupid amounts of value in the window before stim finishes. Or watch how fast zealot/archon/Templar melts with just a few well placed EMPs. But in most real games, by the time ghosts are out in force, so are colossi or disruptors, and the stargates are on the way because the ranged libs are sure to come.
So the resulting matchup isn’t ideal: terran is unhappy because it feels like they are always behind, always losing, and Protoss is unhappy because you can tally up advantage after advantage, but if your colossi are just 30 seconds late none of it matters and you instantly lose.