This was until last year when it was revealed that Ubuntu 18.04 will receive 10 years of LTS support matching up to distros like Solaris 11.3 for industrial applications and servers in the manufacturing and credit card industry.
GetDeb allows its users to receive more up-to-date versions of popular software without upgrading their whole OS or installing from source code.
It is generally advisable to subscribe only to Ubuntu's own package repositories where possible, as software offered by GetDeb and PlayDeb is commonly out of date or unmaintained.
This would require that PlayDeb maintains the packages/forks and could cause conflicts and/or issues with main Ubuntu packages.
Some packages are closed source and can not be recompiled for newer versions of Ubuntu.