Traub TNL 26 CNC Swiss type lathe machines are preferred for several reasons:

1. High precision: These machines are known for their precision, which is critical for producing high-quality, tight-tolerance parts.
2. High speed: The Traub TNL 26 can operate at high speeds, which allows for faster production and increased efficiency.
3. Versatility: The Traub TNL 26 is a versatile machine that can be used for a wide range of applications, including turning, drilling, and milling.
4. Small footprint: The Traub TNL 26 is a compact machine with a small footprint, making it ideal for use in smaller manufacturing facilities.
5. High-performance: The machine is equipped with advanced features and technology which makes it high-performance, capable of handling complex and demanding parts.
6. Low maintenance: The Traub TNL 26 is designed for low maintenance, which can help reduce downtime and increase productivity.

Overall, Traub TNL 26 CNC Swiss type lathe machines are preferred by manufacturers for their precision, speed, versatility, compact design, high-performance and low maintenance.