This is an interesting question, as many people will have different opinions on this. Of course you can teach yourself to draw and there are plenty of resources out there to help you learn. Some of us won’t be able to join a class for various reasons, I have a Resources page to help out those of you in this position.
Personally I feel that a real art class is the best way to learn if you can get to one because there are so many benefits from this type of learning:
Learning with and from others
There is a lot that we can learn on our own, but there is even more that we can learn from being around others. The learners in my classes learn not just from me and all my experience, but from each other. There is something very supportive about being with a group of like-minded people and learning together. Creativity flows in these types of groups where you can see others creating and learn from what they are doing. There is always something we can learn from someone so in a whole class setting you have plenty of people to learn from.
Some of us are able to draw regularly but it is a lot easier when you have a class to go to. Going to an art class gives you the time and space for art, this is hard when you are at home with so many other distractions.
Experience and Skills
A good Art Tutor will have lots of experience, knowledge and skills to share with you and this can speed up the process of learning. If your tutor has taught many learners it is very likely they have seen all the pitfalls that beginners can trip up on. It is also very likely that they understand the process of learning to draw and paint as they themselves have experienced it and taken many learners through it.
It is quite likely that you will make some friends in an art class so even when the course ends you will have one or two ‘drawing buddies’ to carry on drawing with. I see this in my classes often, I have a group of ex-learners who regularly meet up, sketch and visit art galleries together, how wonderful!