AIP ENR says that VFR flights intending to operate in CTA must submit flight details, with the preferred order of doing that being via NAIPS, then in writing, then by phone, and last by radio. It also says you should submit details at least 30 minutes before you expect to enter controlled airspace, and that 'Flight details submitted with less than the 30 minutes notification may be subject to delay.' Some places won't even let you in as a matter of course if you haven't submitted a plan.
If you don't customarily put plans in then using NAIPS can be a confusing and slow process, but once you get used to it, it's a doddle and just takes a minute or two to put a VFR plan in. You can choose whether you want to do that or not, but it's very probably going to make your life easier.