A lot of the "modern" stuff for bass (mostly in the form of solo or accompanied solo works) exploit every register and effect possible on the instrument. It sound airy and thin, but it is a timbre and effect that the composer can exploit, so it gets used.
As a ninth or tenth grade student, I learned the altissimo register up to A above C above high C for a solo competition, and once I mastered that little bit of trickery, every audition group crumbled before me. The novelty of a bass clarinet playing clarinet solo grade music convinced every auditor that I was their fair haired boy.
But, I had my own horn, maintained to my standards, and untouched by anyone else. Our district's musical director, Bob Tobler, told me a few years ago that he would always remember me as the kid who owned a horn that normally only school districts owned. If you keep your instrument out of careless hands (and there are few people more careless than high school bass clarinet players), it's amazing what you can make it do.
Directly behind our house here in Pearland TX lies a two story home, separated from ours by our eight foot cedar fence.. While sitting in the hot tub one spring evening, we overheard the daughter of that family one night as she practiced her school bass clarinet. The next evening, I had my horn out on the patio, waiting to hear her practice. It was fun to mirror her scales on my horn, and then to look at her peering out of the window, trying to discover what was going on in the pitch black void that was our back yard.
Face it: it's not every day that you hear a bass clarinet calling to you out of the night...
The next afternoon, I walked around the blocks and introduced myself to the family, pointing out that I could hear her struggle with notes over the breaks, and offering my assistance.
Her horn, a modern Selmer pro model, had been given the usual school treatment, and had been badly knocked about on the big keys on the lower joint. We took her and her instrument over to my repairman and had him bring it all into alignment, following which she bloomed on the instrument (as most who have these problems addressed do). By the end of her high school career, she was ripping along on my Mozart bassoon concerto transcription, as well as doing a fair job on the Mozart clarinet concerto, all on the bass.
And, i didn't charge her a thing for the lessons...
One of the many errors committed by high school music programs is to assign weak clarinet players to the bass (and, God forbid, alto) slots in their groups. Give an unmotivated musician a hard to manage and poorly adjusted school instrument, and you can't really expect good results. Granted, most of the parts are easy enough to manage - omph-pa-pah and so forth. But, if you then throw a transcription of Bernstein's Overture to 'Candide' at them, you are asking for a botched solo passage, plain and simple.