It is an engineering compromise, just like almost everything is in life. It is basic physics.
The larger cones move more air and hence provide a much more realistic and voluminous bass. However, the larger the cone gets, the less rigid it becomes, affecting the sound negatively.
If you could find an infinitely rigid material, which would never lose its shape regardless of how much air pressure it was exposed to, then you could build infinitely large speakers. But real life has limits :-)
There is also one more very important factor as to why most drivers (and hence the speakers) are smaller these days. It is the WAF :-)
The larger cones move more air and hence provide a much more realistic and voluminous bass. However, the larger the cone gets, the less rigid it becomes, affecting the sound negatively.
If you could find an infinitely rigid material, which would never lose its shape regardless of how much air pressure it was exposed to, then you could build infinitely large speakers. But real life has limits :-)
There is also one more very important factor as to why most drivers (and hence the speakers) are smaller these days. It is the WAF :-)