I think it's more because he's a checking role/depth guy for the team. I'm sure sometimes it was because he needed a kick in the pants, but I think his role with the team makes him an interchangeable part. Now, is that what you want from a former 1st round pick..to be an interchangeable part? Likely not. But, let's not forget this Marlies team isn't an easy team to crack. They are the tops in their division, third in conference, fifth in the league.
I'm interested to see what role he takes next year. Problem with Biggs is that unless some coach likes what he brings to the table in a top-six role, he's unlikely to play in one (at least with the Marlies). He would have to hope names like D'Amigo and Ashton takes permanent roles with the Leafs. Not only that, compete with any newcomers that join the ranks (Brown? Herzog? Rupert? UFAs?).
Personally, I don't think Biggs is an important part for Spott (right now). Think he see more value in other bottom-six types like Carrick, Ryan, and Broll filling a top-six spot rather than Biggs. That's just the impression I get from watching how he uses those players. I don't find Biggs to be a confident player either (heard a few times how hard he is on himself - maybe that's a factor). For me, it's been a flaw of his for a while. He shows glimpses of being a threat, but at the same time can look allergic to the puck. It's kind of a tease. Good news for him is that if he never puts it together offensively he has other translatable skills that could make him useful. One summer of proper training and preparation and you never know what type of turn his career could take..I just wouldn't anticipate/expect a 180 from his current development path.