Full Idea
Newton's reason for embracing absolute space, time and motion was that he thought that universal laws of motions were describable only in such terms. Because actual motions are irregular, the time of universal laws of motion cannot depend on them.
Gist of Idea
Newton thought his laws of motion needed absolute time
Source
report of Isaac Newton (Principia Mathematica [1687]) by Adrian Bardon - Brief History of the Philosophy of Time 3 'Replacing'
Book Reference
Bardon,Adrian: 'Brief History of the Philosophy of Time' [OUP 2013], p.53
A Reaction
I'm not sure of the Einsteinian account of the laws of motion.