As GoldenRivet has stated above; it is a major breakthrough in immersion. Imagine after patrolling for 2 weeks and you get attacked by DCs. I could swear I sensed the smell of fear knowing that those 2 weeks were doing the drill but it was worth. Curious thing: Flight Sim pilots usually do not activate any TC as well even for long flights. They keep themselves busy navigating.
My opinion as I have said before is to get yourself busy (in other words, NOT BORED) by intercepting convoys/single ships in another pc using any other util or SH game (by SH I mean a single mission where a ship will respawn in a certain radius of your sub and then you plan your attack). This way you keep yourself sinking ships while waiting for the "official" patrol to present targets there in the main pc.
Other thing I just remembered is that for those who are playing without map contact updates and also do not wish to see your own sub in the navmap (there are mods for this) you can also load another SH3 or SH4 in the other pc and use its navmap for plotting. Why? In case you want to see the navmap and the periscope at the same time. Just my thoughts here. I dream of one day having a SH6 where I can hook up 3 pcs in LAN and man all stations in multi-monitor support and also save the patrol.