Case 1. Heater provided with no operating instructions in box.
Case 2. Heater could not be programmed. Reason: it was factory set in "Eco-mode" where programming was not possible.
Case 3. Too complicated with layers of programming needed. The A4 sized instructions are many pages long covering many settings and day options.
Case 4. A recent heater seen has a very small window screen where the writing is about 1mm tall and is very difficult to read when programming it.
Case 5. They are too complicated and not easy to use. Over engineered and liable to failure due to complicated P.C.B.s inside. Perhaps that is the plan. If you can't easily use them they save energy as one of my customers found out after spending many hours over the phone speaking with the maker's tech. dept. The heater is now cold and has stopped working.
Z.