Why do I need to pay accrued interest?

Why do I need to pay accrued interest?

If the present bondholder sells his Bonds, he has to get the interest until the date of the sale. Here can be a time gap between the last interest payout he received until he sells them. As the next interest payout goes to the buyer, the buyer must pay this accrued interest to the seller, in addition to the Bond’s selling price.