Let's get this into perspective...
MOST users of zencart are inexperienced novices - that's the beauty of it... people with scant knowledge of software can actually get a functional eCommerce site up and running in a relatively short space of time.
In being novices, they therefore rely on the integrity of the core platform to perform as it is designed to do. They have an inherent and possibly an implied TRUST that the software does what it is supposed to do.
As this software is OpenSource, there are no LAWS that prevent anyone from modifying it in any way they like - including TM - who have their own ways of altering the code structure.
As I said... if you are a skilled coder, and can unpick the way the TM templates are built, then sure... using them is no problem.
But for novices, who have no idea of why an expected function suddenly fails on them, or a setting in the admin panel has no effect in the webshop, these issues can become quite serious... and they then have to hire people to restore functions that they would otherwise have working normally.
FUNCTIONALITY is paramount... (We assign it a value of 90% of a website, with DESIGN being worth only 10%). And we have scores of case studies which prove our point. Some of our most successful clients have ZC sites that are largely based on the "classic" template, where the time put into the cosmetics has amounted to less than an hour's work.
I remain adamant on this (as our considerable experience tells us)... resist the temptation to opt for fancy design at the expense of functionality. The vast majority of web shoppers want an efficient, simple and fast means to make their purchases, and are utterly unconcerned about the "degree of gradient from grey to white" in the site's backgound image...