I can see both sides now, had a cockapoo recently that I got tougher than usual and told the owner it would have to be a shave job or would need to book a second appointment as it would be too stressful for the dog otherwise, luckily the owner was more than happy for it to come back and I know I cut through all the thick matted clumps, in fact got about 90% of matts out but would have been a very long appointment to continue. Trouble is when the matts start felting the choice is either cut through them all, break them up and brush them out which is uncomfortable for the dog (this is what I did, luckily she only had them that bad in a few area's), or you have to go really short to get the blade underneath the matt close to the skin, some groomers get very booked up so may not be able to offer extra appointments, and to be honest at the end of the day shaving them is the kindest for the dog - they don't care what they look like and probably feel great (although you do have to be careful of strong sun when they are that short). There are some tricks to use to try to get a nicer finish but again that takes longer and is for the owners benefit, not the dogs. I don't doubt some groomers do just want to rush dogs through though and do what is quickest and easiest for themselves. I am now on a groomers facebook group and there is a bit of doodle bashing but they are seeing so many badly matted ones now that I guess I can understand why. I tell customers they really need to home groom as much as poss or have 6-8 week appointments, (6 if they matt easily).
One groomer was on there asking advice as she had a nervous cockapoo and she couldn't even get a very short blade under the matts and didn't want to hurt it, posted later saying the owner was going to take it to the vets to be sedated and shaved, a lesson learned there I hope - anyone here?!!