Listing should just be the start of the overall development and marketing plan of the project. If a project simply runs one campaign, then has enough cash to progress that's great, but in terms of multi-round funding and marketing that can reach the target audience it would make sense to run another campaign. it is pretty normal, not doing seems odd.
Coming from a startup oriented background it's surprising that this isn't seen more. It's pretty standard for a startup to go through multiple funding rounds to help fund key milestones in the overall business development plan. It's as if the focus is on getting as much cash off an ICO as possible then sitting on the cash... the thing is we don't seem to see the standard set of White Paper, Market Analysis Report, Investor Prospectus, round a/b/c/ funding and so on that would be expected outside of the crypto space.
It would make a project appear more legitimate and the team engaged for the long-term if a second or third round of funding took place.
CBF