We know that Valve took action to secure our Steam profiles from hackers in November. Valve informed us all that 77,000 accounts get cleaned every month and recommend us to be careful with our valuables.
Valve put three-day-hold on every trade to prevent people hacking our accounts because in that given 3 day, we would be able to understand if something is wrong and prevent it. Now that number has increased to 15.
For each trade, we have to wait 15 days unless we are using Steam Guard two-step mobile authentication. If we use Steam Guard, we will not have to wait for trade and it seems like the reason behind this long waiting period is Valve really wants us to use it. If you are not able to use Steam Guard on your mobile phone, your trades with the players you have been friends with for over a year or more, will only take 1 day.
The only easy way to trade fast is now seem like using the Steam Guard on your phone. If you can't use it, you will play the waiting game. For more detailed information you can visit here.