Lawsmygame

I love my b2b cruises for all the reasons you stated. Especially love this ^^^^^ view too. I stay up late the last night of the first cruise and just smile to myself knowing I don’t have to get up early or leave. I am sad for the people having to leave but so happy I have another week. 

With a booked B2B on Empress my ports don't repeat.
With a booked B2B on Navigator my ports repeat, a double dip to CocoCay and Nassau. 
With a booked Oasis class B3B I'll do Eastern Caribbean, Western Caribbean and then Eastern Caribbean again.  This includes three visits to their private destination. I've been to all the ports before so it doesn't matter.  Pricing was good, reduced solo supplement so 21 days on a ship.  Why not?
I also have a side-to-side or S2S booked.  Take a cruise, debark and move to another ship the same day.  
If I'm spending money on an airplane ticket I might as well do two cruises.
The best part of a B2B is seeing this...

...and knowing you don't have to pack.  

The #1 problem solved is the fact that most cruises are too short.  
For someone who has to fly to a cruise a B2B saves airfare compared to taking two distinct cruises.
B2B allows you to unpack and unwind.  You don't need to take in every show because you can catch one on the next cruise.  
Cruises are great but if you try to do everything offered in one cruise you may end up exhausted and need a vacation from your vacation.  
Take Oasis class.  It's hard to participate in everything offered during a 7 night cruise.  More often than not you have to pick something but miss out on something else.  When you go a B2B you can do some things on one cruise and different things on the next.  Really enjoyed one show?  See it again!
B2B also lets you try different things in repeated ports while exposing you to new ports that are not common to both itineraries.  One visit you can go to a beach and relax, the repeat visit you can go on an ATV or tubing in a cave or you can stay on the ship and enjoy the ship empty of most guests.  
B2B solves the FOMO issue while leaving even more time to relax.
B2B also means one more week of not doing the dishes, cooking or cleaning.  
I have a B3B booked.  Three cruises in a row on the same ship.  B2B is cool, B3B is the next level.