They aren't reliable enough
When the tomtom live works it's up there with the best bit of kit ever. I travel a lot in the SE of England and it's a useful piece of kit. Like I said - when it works.
Here's what happens in my experience at least once a week.........Turn it on - plan a route. Wait for the live traffic to load. It doesn't and tells you there's no network coverage. Turn it off and on again. Traffic might load. If not hold power button for 30 secs to reset device. Traffic loads OK(unless it's a weekend, when there's a fair chance that the server will be down. You won't find this out until after sending a support request - following the instructions to re-format the hard disc - wasting 4 hours of your Sunday afternoon doing this 3 times - only to be told on Monday after ringing the help desk that the server was down). So, having got traffic working I want to connect to my mobilephone via bluetooth. It doesn't pair automatically (I've had 3 different phones and none of them pair automatically with the tomtom) Although you only paired it yesterday it won't pair and just tells you there's no response from the phone. Turn phone off and on - no pairing. Turn TomTom off and on - won't pair. Delete pairing from phone and TomTom. Go through the nausea of the discovery and pairing again. Of course - now you've turned the tomtom off so there's a fair chance that the traffic isn't available (GOTO start).
By now you're either 15 miles up the M3 without having looked at the road once or you've been sitting in the car park for almost 10 minutes and any time the tomtom might have saved on your trip has been used up in making it work. Oh - by the way - if the car park is not on the map (new industrial estate) then you can't do any of the above until you get onto a piece of road that it recognizes -- it just sits in an endless "planning route" loop. You have to drive to somewhere it recognizes, find somewhere to park, then do it all.
The map update service is useful - but beware because it deletes all your favourites, your home and work locations and any map overlays you've downloaded. TomTom will tell you there's a way round this by copying to and from PoIs; it's true but you won't want to do it.
I agree that Nokia will never replace this type of device, and on the rare occasion that I get into the car and it just works it is a fantastic bit of kit, but it's just not reliable enough and the compay is not interested in fixing bugs.