Whilst it would be lovely to get all of our business done early, you have to take into account the calibre of player we are after, and the interest from other parties who are in a similar or better position to us financially. The selling clubs certainly do, as they know our position in the pecking order.
For top echelon players, we can come in with a good bid, but the selling club know that there are other clubs out there that are also looking for this type of player, so you get the inevitable leaks from the sellers, showing that the player is for sale, the deal we are offering, and putting it out there for another club to make a better offer. They can procrastinate for a few weeks to see if anyone else is interested. If no one else comes in, they'll do a deal, but it'll be late.
We do manage to get some over the line early. Despite the angst on here, Romero was actually done fairly quickly, but for a player of his quality that's the exception rather than the rule. Those that get in that kind of quality early, on a regular basis, are those that overpay.