Why should they do that?
HBM is 2-3x more expensive, will the greater bandwidth provided be utilized to offset the added cost?
As on package DDR is already much faster than off chip DDR, there is less of a performance advantage for HBM.
Apple which has been doing on package memory since the M1 continues to utilize DDR standard (they started with LPDDR4X and quickly moved to LPDDR5 which they are still using on the M3). The bandwidth/latency advantage is tunable with on package DDR (High speed and large bit bus width). Commodity parts sure makes more sense to me here. HBM only is worth the cost if the application/use warrants it (H100, A100, B100/B200,etc...).