Yes you may ask why. First off, a normal incident card's leader can reinforce if it is stated in the card and not just a lieutenant. so you are wrong on that only Lts can reinforce
That's not quite what I was saying. I meant that the table is for lieutenants. Other incidents will state their reinforcement costs, which could differ from said table.
second, a friend informed me that the ToI incident cards do state the amount of threat needed to reinforce the ToI monsters for that particular incident.
There you go - until there are lieutenants using ToI monsters, the table itself isn't needed.