Reasons for no suitable Flash/Director port? Money. Market size. Demand.
Lack of demand <= reasons for goodbye to RISC OS in primary education: poor web access (specifically to the content above, eg. at the excellent BBC site); lack of time/will to support two computing platforms within a school; peer pressure to scrap remaining old machines; etc. etc.
I'd also be willing to bet that the onsite support that the likes of RM provide (necessarily given the awfulness of their kit) provide a safety net which is well-valued by the hassled ICT co-ordinator in a small school. AFAIK there are no similar support services offered for RISC OS machines. Even worse, they wouldn't be viable due to the lack of demand - resulting in a horrible vicious circle