Hah. But to be fair, ATM did have a specific use that it worked great for. That is the move to digital voice circuits. The small fixed cell size and built in QoS meant that if you had a fixed line size you could fit X voice channels, and they would all be extremely low latency and share the bandwidth fairly. You didn't need to buffer beyond one cell of data and you didn't need to include overhead beyond the cell headers.

ATM was designed to handle the "future" or digital network needs. But, the immediate use was about voice frames and that likely dictated a lot of the design I'd expect.