While a 1st-order crossover does require fewer parts (perhaps just a single capacitor and resistor) than a 2nd, 3rd, or 4th-order, a loudspeaker with a 1st-order x/o does not necessarily have a simple one. Thiels are often mentioned (as they are above), but they actually have very complicated crossovers. The reason is, their crossovers perform far more than mere 1st-order filtering. There are a great number of parts used to tailor, manage, and compensate for the characteristics of the drivers used in Thiel loudspeakers. Just look at a schematic for one!
On the other hand, the Eminent Technology LFT-8b, which also employs 1st-order filters (one at 180Hz, another at 10kHz), contains only a few extra parts for driver compensation. That speaker’s x/o schematic is posted on the ET website.