Do pacemakers improve the quality of life of people?

Not always. In some cases, it is meant to prevent occasional pauses in conduction, which can occur very rarely. Sometimes they are put in to prevent the first such event, when the likelihood it will occur seems likely, and the patient may never notice a difference! if someone is fainting often, or feeling very lethargic/weak from low heart rates, the pacemaker may have a drastic impact on quality of life.
Yes. Rate responsive and physiological pacemakers have a significant role in the quality of life in appropriate patients.