You could do without the extras and many people do: get their clothes dirty without mudguards, lug a sweaty backpack without a carrier and dodge the police without lights. Or you could add all the missing items yourself. But you’ll find it's much cheaper and safer to have them already on the bike and included under the manufacturer's warranty.
It’s easy to see how someone who doesn’t know a whole lot about cycling, i.e. the average Brit, finds bare bikes most attractive. They look sleeker and on the face of it seem lighter and cheaper. The trade likes to sell that kind of bike because there’s less hassle and more profit to be made from selling those parts as accessories.
The bike-savvy Dutch or German consumer knows this and so the fully-equipped trekking bike is common in Northern Europe; but not here, so it may be difficult to find one that offers the level of quality you desire. The only way to get a truly lightweight frame could well be to add the missing items to an upmarket hybrid.
Remember though, that apart from the extra cost, those accessories add a pound a piece: for mudguards, a carrier, lighting … That bare-bones hybrid may be not be so light after all, since it’s equal to a trekking bike some 1.5kg (3lb) heavier!
In all other respects, a trekking bike is just like a hybrid: same tyres, same brakes and gears, same relaxed upright riding position. The handlebars may be straight like on a mountain bike, or more commonly a curly butterfly-shaped handlebar is fitted to give a choice of handholds. The main effect of this butterfly bar, however, is to facilitate an even more upright riding position – since the brake and gear controls are on the closest part of the bar to the saddle.
If you want to get a bit more athletic on your commute or your travels, consider a touring bike. If on the other hand you want an even more practical bike, free from the mess and maintenance of derailleur gears etc., look at city bikes.