There are many beautiful musical instruments. Each has its own character and style. Learning to play any of them is rewarding and enjoyable. So why would someone choose the piano over another instrument? Why would someone choose a piano for beginners course over, say, a tuba or flute class?
There are lots of reasons to study piano. To begin with, it is one of the most diverse instruments in Western music. A piano player can play almost any style of music. Few instruments have that much range. Who ever heard of jazz oboe or blues bassoon? Yet, piano can be played in classical, pop, rock, jazz, blues and gospel styles, and even more.
Piano is polyphonic, giving it a richness that most instruments don't have. By "polyphonic," I mean that you can, and typically do, play more than one note at a time. In most more advanced piano music, the player plays chords rather than single notes. Even though music written for piano for beginners may not use chords for each hand, beginners' music is still written for each of the two hands to create music independently and in harmony. The two voices of a piano piece, the voice written for the right hand and the voice written for the left, bring a complexity of sound that is unattainable in other instruments.
Piano can be played as a solo instrument, or to accompany voice or another instrument, or as part of a band or orchestra. So with respect to arrangements and orchestration, piano is versatile in a way that many musical instruments are not. Solo tympani, anyone?
Piano trains a beginning musician in a way that other instruments don't. It requires a great amount of manual dexterity, since a pianist needs to be able to use each finger of both hands independently. Even piano for beginners requires a pianist to be able to read both the treble clef and the bass clef simultaneously. Moreover, working with chords and the two different voices played by the two different hands leads to an understanding of music theory and chord construction that most other instruments don't offer.
Of course, there are significant drawbacks to choosing the piano. To state the obvious, pianos are big, heavy and hard to move. Whereas a violinist can pick up her instrument and carry it with her, a pianist can't travel with hers. Even a second-hand piano can be quite expensive. And some smaller homes or apartments are ill-suited for the major piece of equipment that even a small piano is.
Electronic keyboards can offer an alternative to acoustic pianos. Small, portable and relatively inexpensive, electronic keyboards can, at a minimum, provide a means for a student to get through the "piano for beginners" phase and learn appropriate fingering and how to read music. Although they don't have the sound quality that a piano has, a keyboard can be a good choice in homes in which a piano is not feasible.
Ultimately, the real reason to play the piano is because the piano is beautiful. Majestic, elegant and with a tradition of literature unmatched by most other instruments, even an upright piano is, well, grand. Any would-be musician who is trying to decide what instrument to take would make a great choice by choosing a piano.