First, there’s something of an image problem: The harp has a hard time breaking out of its stereotype as a shmaltzy background instrument. Mention harp, and people think of billowing arpeggios used to conjure up dream sequences in sitcoms. There are a few little niches in the musical scene where harp has been used in a more central and muscular way, but these are more rooted in folk traditions (Celtic, Paraguayan), so they don’t get much mainstream exposure. In the classical world, Carlos Salzedo did some very athletic harp arrangements, but most orchestral arrangements have tended to use the harp for filler, if at all.
Then there’s the cost and weight/bulk issue, already mentioned. Beginners, especially children, start on lever harps, not the big pedal harps used in orchestras (levers and pedals are used to adjust the tuning for various keys). They’re much smaller and cheaper, and have a more restricted tonal range, but are otherwise played with the same technique (the string spacing is similar). Someone who learns on a lever harp can transition easily to a pedal harp down the road (although most folk traditions prefer the lever harp for it’s less stodgy sound). A decent lever harp costs about $3000 and weighs around 30 lbs.
Rentals are the way to go in the beginning, as a hedge against a child’s losing interest. These can be hard to come by, and expensive. $60/month is not unusual (I built my first harp to stop the financial hemorrhage when my daughter took up harp). Because rental harps are hard to come by, many teachers keep a small stable of harps that they’ll rent out to students.
Playing harp is not especially difficult. In a way, it’s a great first instrument because it sounds tolerable even in the hands of a beginner (unlike violin, or brass, or woodwinds). Like piano, it’s musically intuitive: the whole array of tonal possibilities are spread out right there in front of you, so it’s a good instrument for acquiring a grounding in musical theory and chord construction. Playing a note is a single action—the plucking of the string—as opposed to the coordinated actions required to sound notes on most other instruments.
Because not many people play it, the harp has a novelty valuer that other, more quotidian instruments lack. My daughter has made some great extra cash by busking out in our little downtown area and at our farmer’s market. People see the harp from far away and are spellbound. She invariably draws a crowd, unlike the poor schmuck strumming his guitar. It’s also easy to get wedding and holiday gigs.