Groovers can be required all over the southwest because the lack of moisture means that nothing deteriorates and also you don't want the peeps wandering all over the place destroying the crytobiotic soils. We've also had to use them in Idaho and Oregon. The population is just getting so high with so many people on the trails that anything hauled in should be hauled out.
Guides and their gear are great when the water for everything for 6 days has to be hauled in over some very treacherous roads. We've done some routes where I sure wouldn't want to be the person driving the support truck.
One thing that is really nice about the mtb tours is that you don't get "tourists." Yeah, there are some clients who get special notes in all the tour companies' files but for the most part they're not too bad because you have to come with a certain fitness and skill level. Kind of like a class 4/5 river trip, you better know what you're doing and the good tour companies will talk to you and access your true skill level; they may not even let you come. The altitudes can be so high also that the tour companies can get concerned. We rode from Telluride to Moab in 6 days on our 1st trip. Day 1 we went over a pass at 10,500 ft and the trip averaged 8,900 ft of elevation. Clients tend to be less obnoxious when they're crawling along clawing for every oxygen molecule.
We only started with tour companies based on the recommendation of friends and have been careful. Asked for lots of information before going, and talked to staff and owners before putting down money. We have had terrific guides who changed routes because they accessed the group and figured out we could handle tougher terrain than the normal routes. We've had guides who had wonderful knowledge of the geology, history, flora and fauna of the area. We've met fellow clients and guides who have become friends that we network with around the country. Guides who served as coaches and taught us new skills. It can be like going to a grown-up's science/bike skills camp.