Why ad-free classics are rare
Sudoku, Solitaire, Minesweeper, and 2048 aren't owned by anyone — anybody can publish a version. That means dozens of near-identical apps compete for the same searches, and at that volume the only business model that works for most publishers is advertising. The game is the bait; your attention between rounds is the product. It also explains the "fake offline" problem: many of these games play offline, but still bundle ad and analytics SDKs that phone home the moment you reconnect.
The ad-free alternatives that do exist usually come in three shapes: paid-up-front apps, free apps with a one-time "remove ads" or Pro unlock, and apps from small studios using quality as their marketing. All three are fine — the point is the developer answered "how does this pay for itself?" with something other than your attention.