It is a way of life which they have chosen to follow and adhere to; therefore the population which chooses this religion must not expect the religion to cater to them, rather for them to satisfy their needs by following the religion, which are completely satisfied(if effort is put in to seek this satisfaction.) And those who consider themselves liberals do not seek to satisfy their needs by following Islam, rather seek to remove bits and pieces from it, in order to make it simpler for them.
here's the definition of liberalism:
a political orientation that favors social progress by reform and by changing laws rather than by revolution
Liberalism requires change and alteration, and since we believe Islam to be a complete way of life, then it does not require change no alteration, and that is why there is no liberalism in Islam; because Islam does not need any changes.
I'd also like to point out that muslims who live and appear more liberal are not bad muslims, nor should we look down upon them, because we do not know if they are in the process of learning and improving themselves.
Peace!