Why isn't it recommend to just use studio monitors instead of bookshelf speakers since they objectively measure better?
I honestly recommend just using active studio monitors over passive bookshelf speakers when performance and price are held constant.
I can think of a few legitimate reasons that favor passive bookshelf speakers, such as,
1. When one prefers wooden or piano black finishes. Studio monitors barely offer those options.
2. When one has to place the speakers on the desk and listen in an ultra nearfield. Many studio monitors have audible tweeter hiss at this distance.
3. When one needs a pair of TV speakers. Studio monitors usually have a bright power indicator light on the front, which could be distracting when watching movies in dim light.
On the other hand, going for studio monitors usually means one would end up spending less on the entire system, specifically on these areas,
1. No external power amplifier needed.
2. Pro audio interfaces are by default balanced, meaning they have a higher output level than unbalanced HiFi DACs while costing less than balanced HiFi DACs.
3. Multichannel audio interfaces are also cheaper than multichannel AVRs and HiFi DACs.
Notice the above reasons all have nothing to do with performance or price but practicability. Studio monitors are actually more convenient and economical.