They should give you 'in-game' benefits as well, though, above and beyond their point value. Things like every future 'military tech' might allow you to upgrade your existing units in hp, morale, attack strength, movement and defense strength! Future 'Social Techs' might increase max population and city size and perhaps give you bonuses for your social engineering settings. Future 'Economic Techs' might increase your gold per turn, give you bonus gold for all your trade routes and/or reduce corruption in your cities. Future 'Industrial techs' will give you a boost to shield output and/or reduces pollution. Future 'Scientific Techs' would give you a bonus to food production, reduce population-based pollution, increase the success rates of Space Missions, and reduce the chance of disease outbreak. Oh and, of course, each future tech you get would contribute points towards your 'Scientific Victory'. Of course, these are just suggestions, but I think this will make future techs very much worth getting, in and of themselves, and convince players to remain committed to the sciences!
Yours,
Aussie_Lurker.