Why raising a periscope did not replace elevated submarine scouting

Why could a surfaced submarine not simply raise its periscope for long-range observation?

The periscope remained far lower than an aerial observer and introduced viewing, stability, and pressure-hull complications when used as a tall surface lookout.

A conventional periscope cannot approach the height of a towed gyroglider. A long raised tube also places weight above a hull whose surface stability differs from that of a normal ship. Another viewing instrument may be needed for reliable surface observation, adding a further penetration through the pressure hull. Rolling and pitching make long-range optical observation more difficult as well. These limits explain why submarine designers explored unusual aerial scouts despite the burden of carrying and operating them.