That's the thing the laws of the game were written as such that there didn't need contact
https://downloads.theifab.com/downloads/laws-of-the-game-2006-07?l=en
This is from Laws of the game 2006/07 to quote....
"A direct free kick is awarded to the opposing team if a player commits any of the following six offences in a manner considered by the referee to be careless, reckless or using excessive force:
• kicks or attempts to kick an opponent
• trips or attempts to trip an opponent
• jumps at an opponent
• charges an opponent
• strikes or attempts to strike an opponent
• pushes an opponent "
With the interpretation of the laws from 06/07 at 3:46 in the below video, Morgan slid through to attempt to trip, there wasn't any contact but none needed, the referee decided that was enough to put Gerrard off his movement.
Since then they have adjusted the law to the below
- trips or attempts to trip
If an offence involves contact it is penalised by a direct free kick or penalty kick
It still makes it grey and vague as ever or possibly even more so but also by putting the phrase "manner considered by the referee" also adds that too as each referee will and can interpret the law differently which is where we lose the consistency.