I don't remember there being infants in the Kegworth crash.
There is a trans-Atlantic divide on the issue of child restraints for children under 2 years old. (I'm referring to the lap belt that loops around the adult's belt). The UK mandate having them, the FAA forbid them.
I'm told the FAA argument against them is based on studies that show the child can be injured if the adult "jack-knifes" over the child. In extreme cases the FAA studies consider them to be only marginally effective in preventing injury. Also, their statistics show that there have only been about 3 infant fatalities since the 70s attributable to children being unrestrained in crashes, therefore there is little to be gained in terms of lives saved by making them compulsory.
The UK (and other authorities) consider them effective in preventing the infant becoming a missile which can injure others. Most studies also show that injuries are reduced when there is less opportunity for sudden movement, hence any restraint like an infant lap belt which loops around the adult belt is better than no restraint at all.