Most countries have similar laws. The US is fairly unique in its strong laws about inadmissible evidence. The argument for those policies is that it stops people being let go on a technicality due to someone signing the wrong form or whatever.

However just because evidence is admissible doesn't mean it has to be taken into consideration. Often the court will decide that certain evidence won't be taken into consideration due to how it was obtained. This is an entirely separate decision than whether or not it should be admissible.