I showed this to my roommate, and he mentioned in his product, the lexer is similarly written. The reason for this is, apparently, it is a really simple way of implementing a finite state machine.
Wikipedia mentions the pattern as well:
"The lex/flex family of generators uses a table-driven approach which is much less efficient than the directly coded approach. With the latter approach the generator produces an engine that directly jumps to follow-up states via goto statements. Tools like re2c and Quex have proven (e.g. article about re2c) to produce engines that are between two to three times faster than flex produced engines.[citation needed] It is in general difficult to hand-write analyzers that perform better than engines generated by these latter tools." (http://en.wikipedia.org/wiki/Lexical_analysis)