they

What does 'they' refer to?

Sometimes all the outcomes customers are trying to achieve
in one area have a negative effect on other outcomes. This is
very common when companies are busy listening to the ‘voice
of the customer.’ Traveling salespeople, for example, may say
they want a smaller cell phone, but they may not have thought
about how hard that tiny phone will be to use. Carpenters may
request a lightweight circular saw without thinking about the
fact that it will no longer have the power to get through some of
the more difficult jobs. When customers make requests for new
product features, they are usually focused on solving just one
problem and are not thinking of how their requested solution
will impact other product or service functions. In this situation,
customers request new features but reject the resulting product
when they realize the ramifications of their suggestions
? the added feature turns out to be worthless because of the
problems it causes.