Air crash report, hard to believe

 I was reading an aircrash report today, I'm not going to give the type or location for reasons that will become apparent soon.
The cause of the crash was seperation of a wing, resulting in loss of control in the fatal accident.  When investigated the home built aircraft was found to have the wooden main spar (which is the wing support) holes drilled out of line, some holes were bigger than others and in one case the hole had been redrilled twice because the bolts wouldn't line up, this resulted in serious loss of strength in the wings.
 What I find hard to believe is anyone making an aircraft for themselves would risk "bodging" the main spar, the wing support, the critical part of the wing.