I know I'm speaking without knowing the full context of Lockwood's life, but one has to think that the money a pro contract would guarantee him would be enticing. He can finish up his degree in the coming years, taking courses over the summer months, and he wouldn't suffer much of a detriment to a career outside of hockey if it turns out he doesn't have a real chance at the highest levels; having signed a contract with an NHL team looks good on anyone's resume, and the money he would make would set him up very well for whatever he might endeavor to do... become an entrepreneur, go onto graduate-level studies, or whatever.
I haven't followed the guy too closely, but considering he's had issues with injuries (shoulder surgeries, iirc?) in the past at such an early stage of his life/career, it wouldn't make full sense to forgo signing with the team--something could go wrong, he could have another set-back, and it might ruin his chances of being signed on at all and by anyone, ever. Also, he's really not that good to begin with. He has the potential to become a Hansen-comparable, but it's not set in stone.
I love this team and have a huge bias, but I genuinely think it's in his best interests to sign at this point, pursuing the dream and, failing that, at least banking some money in the short-term.