Why dishwashers can precisely predict washing time while wash machines can't?

If I select at my dish washer:

• A fixed-time program, it displays 2:20 in the beginning and it runs for exactly 2:20
• An auto program, it displays 2:45 and runs for 2:15 to 2:45 so difference is < 20%

The variation is never in plus meaning that it never runs longer than initial display time.

If I select at my washing machine:

• A cotton program, it displays 4:20 at the start then goes to 2:36 after 10 minutes, but actually can wash between 2:00 and 4:00
• A silk program, it displays 3:35 in the beginning then varies with values, but runs for 1:00 to 5:00 hours.

The variation is many times in plus. The most weird scenario was when it showed 2:00 at 8 pm, but ended its whole cycle at... 2 am meaning that it run for four more hours than predicted.

The above was checked / tested / confirmed on many nowadays and modern dishwashers and washing machines, from many suppliers, including Bosch, Candy, Beko, Whirlpool and many more.

What am I missing? Why modern devices of a one kind can predict running time with the precision to 5-10 minutes while devices of other kind have variations to up to 200-300%? Especially given the fact that boths kinds of devices are doing pretty much the same, i.e. using water and cleaning agent for washing either dishes or clothing.

• My guess is that it's a matter of cost. They surely could tell you the exact time for your clothes washer but it probably wouldn't be a selling feature... you turn on the washer and go about your business. Whereas with the dishwasher, one might be waiting for it to finish to reuse them or put away the dishes and finish up cleaning the kitchen.
– JACK
Jun 15 at 12:14
• It may be that the initial time is based on a presumption of incoming water temp & pressure. If the actual temp & pressure are different from expected, it will take longer to fill the tub and heat the water (if that's done) or wash longer to compensate for lower temp. Remember that there's significantly more water going into the clothes washer than there is the dish washer and that the clothes washer fills & drains more times than the dish washer does, therefore these items have a greater impact on overall run time. `</wild guess>` Jun 15 at 13:02
• @FreeMan that's part of it, but the old part. Generally only the main wash is heated, and possibly one rinse (for all but ancient machines) and filling + heating is a small part of the total time. I can confirm variability with a cold cycle and consistent pressure. Jun 15 at 13:10
• @JACK, see my answer below. They actually couldn't predict the time accurately. To have an accurate time means either wasting lots of water, energy, and/or time (to deal with the worst case) or risking dirty clothes (assuming the best case). You can also interrupt the dishwasher trivially, which you can't do with the washing machine. I often abort the dishwasher programme partway into the drying cycle, and open it if I'm in a hurry (in summer the kitchen is well ventilated and in winter I have a dehumidifier in there, so I'm not worried about steam) Jun 15 at 13:13
• @ChrisH We put a man on the moon and brought him back..... I really think they could predict the time to do laundry if they really wanted to. :-)
– JACK
Jun 15 at 15:03