Further: why use anything other than normal when NOT at a high weight? I don't get this use of improved climb as the 1st choice. There are many companies that don't have these charts because they are unnecessary in their network. They use extra thrust at higher weights. I don't understand the use of improved climb unless at high weights. The same applies to bleeds off. Why not KISS.
Higher PLTOM with the same actual TOM = lower thrust = more engine life
Each operator defines their policies - most A320 operators for example use packs OFF takeoff as SOP in order to increase flex, even if they could depart safely with packs ON. The only reason 737 operators prefer packs AUTO takeoffs is the complexity of the air conditioning panel and increased chance of not detecting wrong bleed system configuration.
What I don't understand is that people are willing to depart at MTOM using improved climb and other methods in order to maximise traffic load (and thus saving money for the company, which would have to rebook pax to other flights, pay for the HOTAC, etc.), but yet are not willing to use reduced thrust with improved climb (when below PLTOM) in order to save the engines by increasing EGT margin (and thus saving money for the company).