When in Lapland - any time of year - not spotting a reindeer is close to a miracle, as they often feed close to roads and habitation. Spotting them while skiing is not unusual, either.
Reindeers are semi-domesticated, and every animal is owned by a herder (or Santa Claus). In Northern Lapland, reindeer husbandry is still a major source of income for many. There are about 200,000 reindeer in Finland and about 6,500 reindeer owners in Lapland.
When visiting in Lapland, you really should try out reindeer safaris. This way you can feel special part of the magic of Lapland just like Santa Claus.