Insulated hose routing means the backpack has a dedicated sleeve for your hydration bladder plus a covered, insulated channel that runs the hose along your shoulder strap. This keeps the hose and bite valve from freezing in cold temperatures—which is a real problem when you're skiing in sub-zero conditions.
If you're doing any backcountry touring or even long resort days in cold climates, insulated routing is worth it. A frozen hydration tube isn't just annoying; it can leave you without water when you need it most. The insulation, combined with blowing air back into the hose after each sip, keeps water flowing all day.
For milder spring tours or mostly in-bounds riding, a non-insulated reservoir sleeve or even water bottle pockets might be fine. But if you regularly ski in temps below freezing, insulated hose routing is a smart feature, not a luxury.