One more reason is that you may have to donate if you want to access restricted rooting methods for latest firmwares. Depending on TV model, here's non-exhaustive list of concerned ones:
E-series 5xxx/6xxx with firmware T-MST10PDEUC greater or equal to 2000.2
F-5xxx/6xxx with fw T-MST12DEUC >= 1120.0, latests T-MST12UABC, T-MST12AKUC
F-7xxx/8xxx with fw T-FXPDEUC >= 1118.0, latests T-FXPUABC, T-FXPAKUC
H-seriesT-MST14DEUC firmware less than 2790 ("less than" means NOT included !!)
T-GFPxDEUC firmwares less than 1290
T-NT14UDEUC firmware less than 1050
ALL other models/firmwares should be rootable. All of them require donation for access. Beware that we have not enough non-European models feedback to provide reliable info. Same goes for some low-ends such as T-NT14M.