Short answer: because you live in an area code overlay in a state that does not have "toll alerting."
Long answer: In an area code overlay, two or more area codes serve the same geographic territory. Two phone lines, even at the same address, could have different area codes. To minimize confusion as to which number you will reach if you dial just 7 digits, and to provide a "level playing field" for new competing local phone companies (more likely to have numbers in the new area code), you have to dial the area code on all calls. However, since you live in an area that does not have "toll alerting" (local calls can be dialed without '1' but all toll calls must be dialed 1+), you have to dial 1 plus area code plus number for all calls.
All of Canada and most of the United States has toll alerting, but there are several large states that do not, including California, New York, and Illinois.
When dialing a number outside your own area code, you typically must dial the area code. In some areas, you also must dial the area code for all toll calls, even within the same area code. Also, in overlay areas you must dial the area code for all calls.
In areas with "toll alerting" (you must dial 1+ for all toll calls), you must dial 1+area+number even if the area code is the same. Many cell phones require you to dial the area code and number to prevent confusion with other nearby area codes. In overlay areas, you must always dial the area code. In some overlay areas, you can dial just the area+number for local calls; in others, you must dial 1+area+number for all calls, local or toll.
You do not have to dial a one after star 67 for out of state calls. You do need to enter the area code.
For outgoing Comcast phone calls. Dial *82 before you dial your intended number to unblock your phone number for one phone call.
No, 911 is a special case. You just dial 911, even if you dial area+number or 1+area+number for other local calls.
Dial [1] plus the area code, and the number itself
Until 25 May 2013 (2013-05-25), you can dial local calls in Saskatoon, and throughout Saskatchewan's area code 306, by dialing only the 7-digit number, although beginning in late February you may get a nagging reminder message suggesting that you dial the area code and number before the call completes as normal. Beginning 25 May 2013, you will have to dial the area code and number (for example, 306-555-0123) for all local calls within, to, or from any part of Saskatchewan. That is in preparation for the introduction of the new overlay area code 639. The 639 area code will serve the same geographic area as the existing 306 area code; namely, the entire province. For toll calls, continue to dial 1 + area + number.
North American telephone area code +1 856 serves part of southern New Jersey, including Camden and Vineland. Local calls within area code 856 can be dialed with just 7 digits, or you can also dial 1-856-xxx-xxxx. Local calls into adjacent area codes must be dialed with 1+area code+number. Toll calls within area code 856 can be dialed with just 7 digits, or you can also dial 1-856-xxx-xxxx. Toll calls to any other area code must be dialed with 1+area+number.
In Alabama, and in many (but not all) states, you must dial 1 + area + number for all toll calls, even within the same area code. If you are on a landline in area code 205 and you must dial 1-205-number, that means that it is a toll call.
Walnut Creek, California, is in area code 925. All calls within area code 925 (local or toll) can be dialed with just the 7-digit local number, or optionally 1 + 925 + number. All calls to other area codes (local or toll) must be dialed as 1 + area code + number.
To place a long-distance call from Puerto Rico, dial 1 + area code + number.
No, there are toll calls within Idaho. To dial a toll call within Idaho, you must dial 1-208 followed by the 7-digit local number, even though you are also in area code 208.