Yes, I understand... Portable Kandrona can be usefull. But look, portable Kandrona and portable pools aren't very little... and not easy to hide when you take airplanes... you can't put it in your bag ^_^'
And I don't think all the Yeerks can have a portable Kandrona. Only Vissers and Sub-Vissers... but no really more... And now, many people should travel for their work, many people travel for vacations... Imagine you're a little Yeerk who should travel, and have no choice... Will you ask the Visser to give you a portable Kandrona? Will you rent it? And how will you hide it from your host's wife and children?!
Not so easy...