What are the reasons why a pragmatic or functional analysis is more advantageous than a pragmatic analysis?

Then at p. 1090 Beetz, J., stated: "The third and perhaps the most important of the reasons why a pragmatic or functional analysis seems more advantageous is that it puts renewed emphasis on the superintending and reforming function of the superior courts. When an administrative tribunal exceeds its jurisdiction, the illegality of its act is as serious as if it had acted in bad faith or ignored the rules of natural justice. The role of the superior courts in maintaining the rule of law is so important that it is given constitutional protection: Crevier v. Attorney General of Quebec, 1981 CanLII 30 (SCC), [1981] 2 S.C.R. 220. Yet, the importance of judicial review implies that it should not be exercised unnecessarily, lest this extraordinary remedy lose its meaning."