Why not?why reinvent the wheel?
Too many projects; too much time
If someone wants to create a rudimentary game engine as a hobby, then that's wonderful but it is as far as he or she will get as a lone developer unless the objective is to use it to make simple arcade games to run in a smart phone. Even then, it probably would target a specific brand of smart phone.
Personal life and your private thoughts always effect your career. Research is the intellectual backbone of game development and the first order. Version Control is crucial for full management of applications and software. The better the workflow pipeline, then the greater the potential output for a quality game. Completing projects is the last but finest order.
by Clinton, 3Ddreamer
Taking the other extreme point of view:
I have an increasingly hard time differentiating all the games made with Unity as they all have a certain look and feel.
You can probably also easily spot a Unreal Engine powered game also.
Cookie cutters gets the job done, don't they? :)
Too many projects; too much time
Even if you leave out aspects of lighting and such, making a game engine is just a great experience to have. The engine I created a while ago in XNA wasn't that good and lacked many features such as lights, shadows, realistic physics etc. But even being able to create an engine that can draw you some sprites, create separate levels and so on is still valuable. Besides, I didn't need any of that stuff for the games I created back then.
If you later on want to switch to a Unity-like engine, it gives you, from my experience, a whole lot more insight into what is happening and can improve the process of learning to work with such an engine in general.
... why reinvent the wheel?
Not only is it a great programming experience, but do you need all the features provided by such engines? Do you need your own scripting language? Advanced 3D physics? Terrain editor? Custom shaders? I bet you don't even need 1% of the features if you want to start making your first games, especially considering that these are usually games like pong. In my opinion, these engines aren't made for such games at all, not in the slightest.
I have no idea what your current level of experience is, but (even though being somewhat dated by now) I still find this to be a great read: First steps into game development.
If you do end up making a game from scratch, Handmade Hero might be of interest.
Hello to all my stalkers.
Yes, you need to pay $1500 for Unity Pro. That's what I meant by "full version". :B
Then you are awfully ambitious for a beginner to think that you will make $100k a year with any of your first games, since that is really the main reason an indie dev would go pro edition ;)
