Here's why:
- It is inexpensive to try out. The Live 9 Intro version is only $99, and if you find that you enjoy the workflow, Ableton offers very good upgrade discounts to Live 9 Standard and Live 9 Suite. Sometimes you can even get it for free! Occasionally websites and magazines offer free licenses to Live Intro, and a lot of MIDI hardware products include free licenses (or at least coupons).
- It has built-in tips and tutorials. You can get information on every element on the screen by just floating over it with your mouse cursor and reading the help text in the lower left of the screen. There's also a Help tab you can open on the right half of the screen where you can find interactive tutorials to help you learn different facets of the application.
- Everything's all in one window. Live has a compact and intuitive user interface that doesn't require you to click through hidden menus or manage a bunch of floating windows to find what you need.
- There's an active community. Live is very popular, and as a result, there are lots of people talking about it online. You can find answers to your questions at many music-related message boards. Strangely, the official Ableton forum has a high number of unhelpful and nasty trolls- although the official Ableton Help page can be useful. Third-party sites such as GearSlutz or even the Something Awful Musician's Lounge are a much better resource.
- There are free and commercial tutorials everywhere. There are a number of sites dedicated to mastering Live, tons of free YouTube tutorials, and lots of great for-pay courses at sites like Groove 3 and MacProVideo. (I especially recommend the MacProVideo courses, even if you're a PC user.)
- It's a real, professional DAW. While I believe Live is the ideal DAW for beginners, it is not a "beginner DAW." It's a full-featured music production environment, suited for original composition with hardware and software MIDI instruments, audio recording, remixing, and DJing.
- It has solid effects and instruments. With the understanding that different versions of Live have different selections of virtual instruments and audio effects, the ones you get are all useful. When I work in Live I use the built-in "The Glue" compressor all the time. While the price may be steep, the Live 9 Suite package is so complete you really could do just about anything you needed to do musically without investing in another software product. (Although I personally would recommend Live 9 Standard coupled with Native Instruments Komplete 9 if you want the biggest possible bang for your buck.)
Overall, though, I don't think there's any better place to start an earnest exploration into music production than Ableton Live.