Easyjet's 737's are either older 300's or new 700's, both of which are smaller than the 800's of Ryanair. That explains the extra seats. Ours no longer recline as recline mechanisms are susceptible to breakage leading to additional repair costs. Maximum taxi speed is 30 knots in a straight line, not fast walking pace as in light aircraft. Your calculations are quite correct, however let's not forget that 2 extra minutes per flight with the incumbent additional fuel burn multiplied out by thousands of flights per year adds up. Also, that extra two minutes taken taxiing out just might delay the aircraft an extra few minutes due to landing traffic and even greater delays if due to missing a slot.
Please understand that we don't do anything without a reason and we ARE thinking about the operation continually. Thank you for your observations.