Cost is absolultely why they do not put on better shocks, but its not just Triumph, every manufacturer shaves costs on the suspension. There are some that put really good stuff on their bikes, but that is the exception not the rule. the other area is exhaust. Every company knows one of the first things people do is trash the restrictive heavy exhaust and put on better stuff.
It works well in that case, jam crap in there to make it Euro 4 compliant and sell the bikes, people spend some coin get good exhaust and get to experience the bikes as they were meant to run