Practical experience is not merely the ultimate test of ideas; it is also the ultimate source. At their beginnings, most ideas are dimly perceived.
Ideas are most clearly viewed when presented as abstractions, hence the common assumption that academics — who are proficient at presenting and discussing abstractions — are the source of most ideas.
One of the dangers in our system of formal education, however, is that a student can go all the way through to an advanced degree in many fields without ever having seen an idea in the rough. An academic with this kind of background may even have trouble recognizing a new idea when he has one.