It depends - an increased frequency can (depending on the market) generate additional use of buses.
The claimed 'attraction' of mini-bus services in the deregulation era was probably more a result of the frequency increase that usually went with it rather than any intrinsic appeal of minibuses.
It is generally accepted that a frequency better than every X minutes will mean people don't think about whether a bus might be due, they just go to the bus stop and know there will be one soon (X varies between 10 and 15 depending who you ask) - obviously that sort of frequency isn't going to be possible outside larger towns.
The Tillings Group (of which Western National was part) tended towards relatively infrequent interurban services, often at infrequent intervals, with odd deviations off the main route on different journeys / days of the week, and put duplicate / relief buses on the busiest journeys.
While those odd frequencies and deviations served genuine purposes (albeit in some cases many years after that purpose still existed) they did make it difficult to sell the service, and required a degree of thought before going to catch the bus. If someone genuinely has a choice how or whether to travel, then a lot of thought about what day of the week it is, whether it's a school day and if so in which town, and so on, tends to discourage bus use...
There are a number of interurban routes in Lincolnshire, for example, where the rural bus grant era led to a major re-vamp of trunk interurban routes that had run a few times a day, most of which now run (at least weekday daytimes) hourly. While much of the rural bus grant (etc) money has dried up, most of those trunk routes are still going on a commercial basis.
Obviously the potential of each route will be different (hence a need for local decision making rather than a lot of diktats from on high, which is somewhere that First weren't always great) and there are one or two such routes in Lincolnshire that didn't do so well...