I partly agree.
Though I did see a quite elderly couple walk straight up to the Self Service Terminal and check themselves in today...so they aren't all computer-shy.
The reason BA Connect seemed to pre-assign you together was that Manx Regional staff, mostly ex Manx Airlines old-school superstars, would go through the bookings the night before and manually put you all together for the next day. Way beyond the call of duty and something they never got enough thanks for. The Flybe system doesn't give you that nice option.
However, the reality is the check in staff at IOM do a sterling job of helping folk sit together. The flybe shares system does automatically spread you about, primarily to make sure the a/c trims perfectly, no matter where or how many no-shows occur. The Staff on check-in "force" the system for couples and families by swapping seats manually to get you all together, and when the loads are high, the last ones to check in simply have to lump it. to get them together would mean asking couples who made the effort to check in in good time to split up and that's not fair really.
The extra charge allows you to effectively short cut the bit about checking in early. Good for families like us who are nearly always lastminute.com on such occasions....
But like any business, additional services = additional revenue streams. That's the modern way.