Solomon has an agenda for each of the types of people he addresses.
To the simple, he offers a gift: prudence, knowledge and discretion (Prov 1:4). You can’t stay at the crossroads forever. Not to make a decision is to make the wrong decision. Turn to the Lord (trust in his Messiah, Jesus); start moving toward him and becoming like him. Then you’ll live up to your created potential, and you’ll obtain your redeemed glory.
To the foolish, he offers a challenge: fear the Lord and begin to have knowledge (Prov 1:7). Be a fool no longer. Give up what you cannot keep (your own self-satisfied condition and individualistic righteousness) to gain what you cannot lose (entrance into the eternal kingdom, fullness of life, most delightful joy). It will cost you everything and be the most difficult thing you ever do, but it’s the only way to true freedom and lasting insight. Jesus died a fool’s death so fools could know the wise life by knowing him.
To the wise, he offers both encouragement and caution: you’re running on the right path, but don’t slow down (Prov 1:5)! You’re never finished. You haven’t arrived yet. Wisdom is not something you are; it is something you are doing. We can never be wise; we can only become wise. It’s a journey, not a destination. The wise person grows closer and closer to the Lord Jesus until the last day.