Because brakes and suspension are two different things altogether.
The brakes on the sixty series trucks are fair at best. By extending the brake line with an additional brake hose for a very modest price does not compromise or degrade the system in any way. I have read about people having issues with extended length stainless lines that they paid a premium for. I didn't say that my way was the only way to do it and that all other ways are ****, I merely offered up another option.
If you were replacing the entire brake system from M/C to wheel cylinder/caliper and all the hard lines in between, then I would go with a nice flex line. But unless you're doing that, then IMOP there is no reason to break the bank on one small component that won't make any difference on the braking quality.
See link below:
How to Make Toyota 4x4 Extended length Brake Lines for lifts and long travel suspension. - YouTube