I don’t think added ports is likely the main reason; the battery capacity of 14" is 20% bigger than that of 13" which should account for much of the difference. Other reasons may include larger heat pipe and simply larger dimension all round.
- Weight: 1.4 kg (13") vs 1.6 kg (14") - +14%
- Internal volume: 1007 cu cm (13") [1] vs 1071 cu cm (14") - +6.3%
- Density: 1.39g/cu cm (13") vs. 1.49g/cu cm (14") - +7%
- Battery: 58.2 Wh (13") vs. 70 Wh (14") = +20%
[1] Likely smaller than this due to the tapered design
It’s really hard to compare the MBP with laptop of another maker since the materials used, build etc. are vastly different. Laptop design is basically a set of trade-offs and I guess Apple is willing to increase weight and volume in exchange for other desirable qualities (larger screen and battery, greater degree of rigidity - still yet to find another laptop keyboard that is so rigid).
As for chargers, personally I am reluctant to use a third-party charger with the MBP, esp. when it is still under warranty. I use a 30W MacBook Air charger (as mentioned in the thread you started earlier) and find it adequate, but that is just me (and I can afford the time to stay plugged in for a while).