What exactly is so slow about encoding on CPU? In my career working with video encoding I haven't seen any big latency differences between where the encoding wa

What exactly is so slow about encoding on CPU? In my career working with video encoding I haven't seen any big latency differences between where the encoding was happening - if anything CPU was often better at latency just because it supported more "wierd" encoding schemes (Intra refresh, partial encode) that were better for latency than GPU encoding blocks.