You do realize I am that "few" that keep my house heated to 26-28 degrees CELCIU?s. -checks- which is between 78 and 80. I live in Canada. Now, if I do not have my house that hot, the basement room is kept at 28 even. Therefore heaters are optionary.
Decorations are optional, they did add plants after the picture was taken (as mentioned, re-read if you deny). I have used some "hiding spots" for some bettas and they do not use them. Others always use them to sleep in. Know your OWN INDIVIDUAL BETTA, and you do not need to do what every Jon or Jane does.
Just to mention, a better way to phrase it instead of saying YOU HAVE TO which comes across as pushy, try saying "Just make sure not to let the temperature drop beneath 76, because bettas do so much better in warmer water! Do you have any fabric plants in your area? I have some and they are awesome!" Be encouraging, not discouraging. Because TEXT DOES NOT HAVE TONE, the way everything is typed, is read differently by every single person on here.