@soix A lot of manufacturers don’t want to produce a circuit that they didn’t design, the exception being classic circuits from decades ago.
IME having a direct-coupled output at the preamp level is a boon for detail and neutrality, even moreso than at the amplifier output. The coupling caps at the output of most tube preamps are usually the most expensive that will be in the circuit. They are usually a compromise of being as large as they can be to accommodate solid state amps with a lower impedance input, while at the same time as small as they can get away with so that the inductance of the part causes the least amount of coloration. This often limits the preamp as to the lowest input impedance they can drive without loss of bass. When you direct-couple, you get the bass and detail at the same time and no problems driving low impedances. My speakers are 16 ohms and fairly efficient; I've driven them directly with my preamp and while it won't play much above a conversational level, it sounds fine and controls the dual 15" woofers with no worries.
IME having a direct-coupled output at the preamp level is a boon for detail and neutrality, even moreso than at the amplifier output. The coupling caps at the output of most tube preamps are usually the most expensive that will be in the circuit. They are usually a compromise of being as large as they can be to accommodate solid state amps with a lower impedance input, while at the same time as small as they can get away with so that the inductance of the part causes the least amount of coloration. This often limits the preamp as to the lowest input impedance they can drive without loss of bass. When you direct-couple, you get the bass and detail at the same time and no problems driving low impedances. My speakers are 16 ohms and fairly efficient; I've driven them directly with my preamp and while it won't play much above a conversational level, it sounds fine and controls the dual 15" woofers with no worries.