You're right that Ti has a drive to "understand" people and things and the world. So, I understand people, but I sometimes fail to understand "why". For instance, I understand that my ESTJ step-father likes to work 7 days a week, virtually all day. If he has time off from his business, he goes in the garage and works or finds something around the house that needs fixing - and works - like sweating in the sun, tired at the end of the day, etc. I understand that's how he is - but I fail to see "why" anyone would want to do that.
My ESFP brother works 2 jobs and then parties until 3am in the morning, then goes to work the next day and can't even keep his eyes open cuz he's so tired from partying the night before. Then, the next night - he parties again and loses more sleep. And so by the end of the week, he gets sick and feels like crap. Instead of getting some rest while he is sick, he goes to more parties and gets more sick. I understand that he is this way, I just fail to see "why" anyone would continue doing that.
Yes, I know. Ti is like the grinch that stole Christmas. Sue me.