Need for startprefix script in gentoo prefix?

[cdebanil]

After installing gentoo prefix, why can't we just add the ${EPREFIX}/usr/bin and similar directories to PATH variable in .profile? What is the need to use ./startprefix everytime we want to use packages installed in the prefix?

[Genone]

From quick glance it does some additional sanity checks and environment cleanup. Wether that is strictly required or just a precaution I can't say.