Virtually all tyres are now fitted without inner tubes but this does not mean they should be considered obsolete. Also, unless you have owned the vehicle for a considerable time, it is entirely possible that a previous owner had one or more tyres fitted with tubes to overcome the problem of a sightly damaged rim or a cracked tyre wall and so on.
In an extreme case where you are forced to effect a repair yourself, a tube might be your lifeline. This is not as silly as it might sound. It will not be the first time that TWO punctures occur on a bad stretch of country gravel road when you only have ONE spare. In country like that, it is wise to be prepared for the worst and just having repair plugs may not be enough.
Even if you are not that far from a town when a problem occurs, the local tyre dealer may not carry your brand or size of tyre, so unless the damage is beyond any repair, having an inner tube handy might save you having to purchase a different brand of tyre just to keep you mobile. Constant 4WD vehicles must NOT have different sized tyres so you may be forced to change all four – an expensive fix when there may be a cheaper solution. A patch and an inner tube will probably get you home, or at least to a dealer who can match the other tyres already on the vehicle.
A final note about valves. It is now standard to use those round plastic covers over the valve stem and they do NOT have the tool requires to remove and replace a valve. In fact, it is not easy to find a valve tool so buy or scrounge one from a friendly tyre dealer to carry in your tool kit. Like many tools, you may never need to use it, but if you do, virtually no other tool will do the job!