The only reason they're not "spammed" in 1v1 is because you'd never need more than one. Sherman's/ Pershings are only rushed to exploit a timing window before OST has armor presence.
Tds are useless vs lone capping squads. Everyone in one's runs around with p4's, shermans, or t34s hitting cap points. People use these tanks to hit lone capping squads away from the enemies main army. This works because players don't take their at guns to the edges of the map. When the enemy turns their army to counter your lone medium, you bring your medium to the other side of the map. Tds are only built in response to armor that mediums or at guns can't take on. You won't be able to prevent panthers from hitting your sneak-capping-infantry with mediums or at guns. You need something to chase it down from one side of the map to the other if the situation needs it.
The problem is clearly not in one's, but one's is usually the game mode that gets balanced, so people lie on the forums to make it sound like the issue is with one's also. Most of these changes are more 2's or up type changes. If td spam were an issue in 1's, we would be seeing this abuse in every 1v1 tournament, but we don't. So simply say this is 2's and up to avoid confusion.