EskimoBlu - I get you on the added air and equipment requirements, and how the convenience of not looking looking out for someone else can allow you to dive without interruption, BUT...unless you’re a dive professional working with clients or students, why would you ever need to monitor anything but your buddy’s location and basic well-being? Further, if you’re diving the same profile, you’ll have very similar, if not identical bottom times - So there goes the notion of checking your buddy’s computer / bottom timer: it’s unnecessary. Buddy dragging you to the surface in a panic? Let him/her go on their own if that’s what they’re so set on doing if you can’t take positive control of their buoyancy: Yank a fin if they won’t stop swimming - All these things we cover in the basic Rescue Diver or Stress & Rescue course (Which is a great supplement, if not prerequisite to your Solo Diver certification). Your arguments are moot except for the case of supporting a 2nd diver while making decompression stops. Even so - Rule of thirds (if you’re following them) should provide enough gas to handle an equipment emergency and some stop is better than no stop for the troubled diver. You’re already well aware of not depleting your own supply to such a level that you can’t ascend safely on account of another diver. I push this emphasis all the way down to my basic Scuba Diver or Open Water Diver students. In the end, you make decisions based on the collective best interest of the situation, without disregard to your own safety.
Critical thinking:
How can you rescue yourself from an underwater blackout or serious laceration where you’re losing blood from someplace you can’t apply pressure to? How do you recover that weight belt that came dislodged and lies 20’ below you as you’re hanging onto the last rock or wreck railing holding you from an uncontrolled ascent in a 7mm Farmer John? The answer is: You can’t; you won’t - and that’s where you’ll most likely find an appreciation for that buddy you’ve painstakingly had to keep track of for the past 35 minutes.