One might argue that the Trill as a species were being accused here, and the accused should have no say on how they are judged.
That is, there would be plenty of Trill
precedent of the Trill committing crimes and being judged for it, but what the Trill did with or to each other would not be of any interest to the Bajorans - and what the Bolians or the Cardassians in the past had judged about the Trill criminals they faced would not be relevant, either. Bajorans and Bolians would simply have different and often incompatible ideas about justice; strange foreign ways would not satisfy Bajorans.
Any ideas how the Symbionts reproduce, or how long a symbiont can live for?
Considering how willingly Dax in this episode seemed to throw itself at the (lack of) mercy of the Bajoran court, without any attempt at a defense, one might argue that Dax was old for a Trill, and for that reason uninterested in what the next fifty years would bring. A couple of hundred years would then be a good guess for a lifespan.
Other Trills of comparable age might be daredevils for the same reason of approaching death. Or they might have become death junkies, enjoying the rush of their host dying. It's a bit difficult to see why the hosts would be interested in this joining thing if all Trills were like Dax or Odan, but perhaps those two were old geezers the likes of which a host candidate would rarely face?
Procreation might be something left to the unjoined Trill, in those underground milk pools. We never learned whether the symbionts recognized the concept of family or pedigree; perhaps they don't even know who their parents are, and it's all conducted much the same way the fish spawn here on Earth?