Because if you don't you will truly be disrupted.
By accepting it, the disruption easily becomes part of the leisure time, though somewhat differently.
It is the acceptance which allows you to embrace it.
It may then transform the so-called interruption into an adventure or curiosity.
Besides, if the interruption calls for you to be patient, forgiving, tolerant, allowing, or loving, you don't have to do anything to do them - just not interfere
So in essence, it really is not an interruption, just somewhat different.
In the past, if someone interrupted me, I would get incredibly irritated. I wouldn't lash out or anything like that, but it would definitely upset me visibly. I eventually realized that people don't interrupt me intentionally and more often than not whatever I was doing wasn't that important that I couldn't be interrupted, so there's no need to get upset over it. As Visitor mentioned above, I would just accept it for what it was and continue whatever I was doing after I was done with the interruption.
If I noticed the interruptions were frequent, I would talk with the person who's interrupting and explain calmly but firmly that the interruptions were taking me out of what I was trying to do. If the person is understanding, they'll give you your space with no issues. Sometimes the person won't be understanding, though, and will probably get upset with you over it. You'll have to handle that separately as it depends on who you're dealing with.
As an aside, one thing that greatly helped me get over my irritations was meditation. I find myself generally calmer since I started meditating daily, and these irritations happen far less frequently. I just mention it in case it's something you might be interested in trying if interruptions are causing anger or something among those lines.