Whereas in Byzantine agreement (of which Byteball is an example), then when sufficient witnesses stop responding (or collude to respond towards divergence), then the system can't become unstuck even if the token value declines.
Bad witnesses can be replaced.
With Bitshares' DPoS (also in Steem), the whales can vote in new witnesses at any time, so it can't get stuck unless the whales decide to destroy it.
Same with byteball, only replacement mechanism is different.