By itself, this is an argument from silence. Driving could be a sin, typing could be a sin. This does not, however, determine whether something is sin or not, it determines whether or not something is against your conscience. Something that is wrong for you is not sin, it is wrong for you. Then it is wrong for you. None of this makes it sin. Many studies show that it has many health benefits: for the prostate, for stress relief, and it can even be a sleeping aid. So yes, it is beneficial. Type in 'masturbation benefits', you'll get tons of good results on the first page. Food can be addicting, so can alcohol. Yet neither of them is condemned in the Bible, just the excess of them.
We depend upon food and water for survival, as well as shelter/an ideal temperature. These are all physical. While they may be brought about by God, they are not necessarily caused by God, meaning that we do not, in fact, only depend upon God. Also, where is this verse that says God is all we need? And if that is the case, why has psychology shown the need for human contact to maintain psychological equilibrium? Your opinion is great for you, but it does not dictate what is or is not sinful: only what is wrong according to your conscience.