Continued DE bombardement actually tends to do more economic damage than Novalith bombardement on similar scale.
Reasons being that Novalith is highly ineffective once SB is in place..... yes it does still hurt but the effect on a late game economy is rarely more than a slight dent.
On the other hand, loss of allegiance does reduce extractor income too..... and every 100 lost extractor is 450 lost credits.
Most importantly however is, that your enemy is forced to scuttle a considerable ammount of tradeports to avoid culture loosing his planets. That is some highly underestimated eco damage, especially as it is longterm.
Especially nasty in capital victory now.... enough DE shots WILL destroy your capital... no matter how many culture centers you have.