Why isn’t 1 + 1 = 2 in internet bonding?

The principle of aggregation is to maximize bandwidth by taking advantage of the multiplexing ability of the network. In theory, 1 + 1 = 2. However, additional “costs” are incurred when splitting and merging the data stream during internet bonding. Therefore, 1+1=2 is not always the case. The best aggregation to achieve is approximately 1.5.

You can find more about bonding here: Internet bonding service