Ms McQueen-Watton believed some parents still hadn't learnt to carry children correctly.
"Some parents have got the message, but if you look around at cars parked in the supermarket, there's still a lot of parents not using restraints correctly.
"There's probably a bit of naivety, in that parents don't know what they need to do, and a bit of the 'she'll be right' attitude when they take short trips."
Cost was another factor, she said.
"Car seats aren't cheap so parents might keep using a restraint that their child's grown out of because they can't afford to replace it."
The number of Plunket sites offering car seats has declined from 283 at its peak in the 1980s, to 72 today.
Despite efforts to make the service sustainable, sites across the country have been closing as they can no longer afford to operate.
The majority of these sites only operate part time, a few hours a day, several times a week.
"The decline indicates families' needs have changed," Ms McLeod said.
When Plunket started offering car seat and capsule hire in 1981 just 20 per cent of children were buckled in. That number has risen to 93 per cent.
However, recently released data by Safekids Aotearoa showed car crashes were still a major cause of children's injuries and deaths.
Between 2006 and 2010, car crashes were the second most common cause of children's deaths - second only to suffocation.
Safekids Aotearoa director Ann Weaver said the number of car crash deaths was far too high.
"In most cases, the deaths were totally preventable," she said. "Most parents use car seats but a lot aren't installed correctly.
"Most countries only have one standard for car seats but, in New Zealand, there's four - American, European, Australia/New Zealand and Japanese.
"We also import cars from a number of different countries so getting the right car seat for a car can be difficult."
Safekids believed children should be restrained until they are 148cm tall, she said.
"Seatbelts are designed for people 150cm and over. At the moment, kids have to be in restraints until they're seven, but most aren't 150cm tall by then."
Ms Weaver said it was sad Plunket's car services were ending but she believed there was enough other reasonably priced retailers parents could buy or hire car seats from.
Plunket will still work in car seat education, but the scale of this work has yet to be decided.