See, this a very interesting observation to me.
When I was using EBS and helping out at the shows and stuff, I used to literally scream at them, they need a lightweight, tiny head to go up against Markbass and the emerging small heads. EBS at the time simply weren't interested. They eventually caved, about 6 years later... with the Reidmar - which despite being an awesome amp, hasn't got the same small factor appeal.
Their best selling amp at the time was the Classic 450, a big retro 14kg head. They were shifting loads of their gear in Sweden, Germany and along with growing sales in the US where the TD650 was where it was at. Their stuff, especially the Classic 450 and their valve amp (T90) was literally doing nothing in the UK because everybody wanted portable. Pretty much only the HD350 was selling in the UK, albeit in small numbers. According to their sales figures, these heavyweight amps (and bigger cabs) were selling great in their homeland and Germany... just not in the UK.
So if you look at Peavey and their immediate demographic, where the Americans love big and heavy, maybe it made sense for them to not change the formula. Then when they realise they failed with what they had... they went with the Elf after a bit more market research.